Discrepancy in Calculating Average Ratings from Java Spring boot Rest api

I am working on a project where I need to calculate the average ratings from MongoDB data using Java. However, I'm facing an issue where the calculated average does not match the expected result. I have reviewed the code and the data, but I'm unable to identify the cause of the discrepancy.
The average rating I obtained from the calculation is 1.309375 However, based on the provided values, I expected the average rating to be 3.325 if I haven't forgotten how to average the results.

this is the document in mongodb review summary

Here is the code I'm using:

 public Page<Movie> allMovies(Pageable pageable) throws Exception {
        Page<Movie> movies = movieRepository.findAll(pageable);
        List<ReviewSummary> reviewSummaries = reviewSummaryRepository.findAll();
        int numRatings = reviewSummaries.size(); // Moved this line outside the loop
        Map<String, Double> avgRatings = new HashMap<>();

        for (ReviewSummary reviewSummary : reviewSummaries) {
            String imdbId = reviewSummary.getMovieImdbId();
            double rating = reviewSummary.getRating();

            if (!avgRatings.containsKey(imdbId)) {
                avgRatings.put(imdbId, rating);
            } else {
                double totalRating = avgRatings.get(imdbId) + rating;
                double avgRating = totalRating / numRatings; // Changed reviewSummaries.size() to numRatings

                avgRatings.put(imdbId, avgRating);
            }
        }

        for (Movie movie : movies) {
            String imdbId = movie.getImdbId();
            if (avgRatings.containsKey(imdbId)) {
                double avgRating = avgRatings.get(imdbId);
                movie.setAvgRating(avgRating);
            } else {
                movie.setAvgRating(0.0);
            }
        }

        return movies;

    }

this is what i get in my postman get request for a movie

"imdbId": "tt8760708",
"title": "M3GAN",
"releaseDate": "2023-01-06",
"trailerLink": "https://www.youtube.com/watch?v=BRb4U99OU80",
"poster": "https://image.tmdb.org/t/p/w500/xBl5AGw7HXZcv1nNXPlzGgO4Cfo.jpg",
"genres": [
"Science Fiction",
"Horror",
"Comedy"
],
"backdrops": [
"https://image.tmdb.org/t/p/original/5kAGbi9MFAobQTVfK4kWPnIfnP0.jpg",
"https://image.tmdb.org/t/p/original/dlxzUj7z1MqEcFiwvvrj0bvBKDY.jpg",
"https://image.tmdb.org/t/p/original/q2fY4kMXKoGv4CQf310MCxpXlRI.jpg",
"https://image.tmdb.org/t/p/original/pTxwFdsdDWzpCRYuk1QbggdaOlL.jpg",
"https://image.tmdb.org/t/p/original/1zuz2RgFoOjulkjjNHHFc3WiHGB.jpg",
"https://image.tmdb.org/t/p/original/7HqxI1IXMloT9VTSuDC8ikaj810.jpg",
"https://image.tmdb.org/t/p/original/vpK2rp3J5LiC01HoNM0j9DEHQ1T.jpg",
"https://image.tmdb.org/t/p/original/cNHXdmr4amP6EPCMa0dqD8rwzDV.jpg",
"https://image.tmdb.org/t/p/original/txQLFd6rfQrskQhFENkS1jElptt.jpg",
"https://image.tmdb.org/t/p/original/dC4tj1ONdlZ2TWv4XD2SA1KUnJN.jpg"
],
"reviewIds": [
{
"id": {
"timestamp": 1683393168,
"date": "2023-05-06T17:12:48.000+00:00"
},
"userEmail": "arnold@gmail.com",
"movieImdbId": "tt8760708",
"rating": {
"id": {
"timestamp": 1683393168,
"date": "2023-05-06T17:12:48.000+00:00"
},
"userEmail": "arnold@gmail.com",
"movieImdbId": "tt8760708",
"value": 3.5
},
"body": "Seem a bit meh "
},
{
"id": {
"timestamp": 1683393413,
"date": "2023-05-06T17:16:53.000+00:00"
},
"userEmail": "john@gmail.com",
"movieImdbId": "tt8760708",
"rating": {
"id": {
"timestamp": 1683393413,
"date": "2023-05-06T17:16:53.000+00:00"
},
"userEmail": "john@gmail.com",
"movieImdbId": "tt8760708",
"value": 3.5
},
"body": "Seem a bit meh "
},
{
"id": {
"timestamp": 1683393446,
"date": "2023-05-06T17:17:26.000+00:00"
},
"userEmail": "jim@gmail.com",
"movieImdbId": "tt8760708",
"rating": {
"id": {
"timestamp": 1683393446,
"date": "2023-05-06T17:17:26.000+00:00"
},
"userEmail": "jim@gmail.com",
"movieImdbId": "tt8760708",
"value": 2.0
},
"body": "good enough "
},
{
"id": {
"timestamp": 1683393489,
"date": "2023-05-06T17:18:09.000+00:00"
},
"userEmail": "will@gmail.com",
"movieImdbId": "tt8760708",
"rating": {
"id": {
"timestamp": 1683393489,
"date": "2023-05-06T17:18:09.000+00:00"
},
"userEmail": "will@gmail.com",
"movieImdbId": "tt8760708",
"value": 4.3
},
"body": "very good"
}
],
"ratings": [
{
"id": {
"timestamp": 1683393168,
"date": "2023-05-06T17:12:48.000+00:00"
},
"userEmail": "arnold@gmail.com",
"movieImdbId": "tt8760708",
"value": 3.5
},
{
"id": {
"timestamp": 1683393413,
"date": "2023-05-06T17:16:53.000+00:00"
},
"userEmail": "john@gmail.com",
"movieImdbId": "tt8760708",
"value": 3.5
},
{
"id": {
"timestamp": 1683393446,
"date": "2023-05-06T17:17:26.000+00:00"
},
"userEmail": "jim@gmail.com",
"movieImdbId": "tt8760708",
"value": 2.0
},
{
"id": {
"timestamp": 1683393489,
"date": "2023-05-06T17:18:09.000+00:00"
},
"userEmail": "will@gmail.com",
"movieImdbId": "tt8760708",
"value": 4.3
}
],
----> here is the issue     "avgRating": 1.309375,
"predictedRating": 0.0,
"similarity": 0.0

You shouldn't be dividing by total number of ratings (numRatimgs) [this is what causing issue for you]

double avgRating = totalRating / numRatings;

Instead you should divide it by actual number of occurrences of that particular movie until that time.
May be you can have a pojo called MoviRating where you can have properties inside it like - totalReviews,totalRating and averageRating
In your map you can have data as <String, MovieRating>
And keep updating the data in pojo.
Hope this helps you.