SQL - Select all Entries where the difference between Characters at Position 10 and Position 20 Equals 1?

I work in a factory that manufactures electrical sensors.

We manufacture the Sensors in Batches (there's 10,000 Sensors in a Batch).
The Batches are referred to by Numbers like 1000585855; with the last 6 Digits being unique to each Batch.

The first stage of manufacturing the Sensor however (on a machine called Dispense), involves two Batches being processed together.

Generally, the Batches only differ by the last digit being +1 larger.
So for Batch 1000585855, the 'sister lot' will be 1000585856.
(When we reference these Lots being processed on Dispense in the Database, they are quoted as 1000585855_000585856.)

Occasionally however, the sister lot may be +2 or +3 larger (really it can be + any natural number).
So for example, I have seen 1000456872_0000456874.

The information relating to the batches is stored in an Oracle Database Table.
The Table is called the EM_EQUIPMENT_LG Table and is structured like so:

Is it possible to construct a Query, whereby I obtain the BATCH_IDs, only where the difference between the 10th and 20th Characters (Bolded) is greater than 1?

So, if I was to utilise such a Query in the above example table, the only BATCH_ID returned should be 1000731637_9. (As 9 minus 7 = 2)

WITH			--	S a m p l e   D a t a :
	tbl (EQUIPMENT_ID, BATCH_ID) AS
		(	
			Select 'Dispense', '1000731655_000731656' From Dual Union All
			Select 'Dispense', '1000746832_000746833' From Dual Union All
			Select 'Dispense', '1000731637_000731639' From Dual Union All
			Select 'Dispense', '1000575235_000575236' From Dual
		)
--	M a i n   S Q L :
SELECT  EQUIPMENT_ID, BATCH_ID
FROM 	tbl
WHERE	To_Number(SubStr(BATCH_ID, 20, 1)) - To_Number(SubStr(BATCH_ID, 10, 1)) > 1
--	
--	R e s u l t :
--  EQUIPMENT_ID BATCH_ID            
--  ------------ --------------------
--  Dispense     1000731637_000731639

Maybe it would be better to take two chars like 9th and 10th with 19th and 20th as there could be some problems with numbers ending with 0. Used To_number() because I dont like to be dependant on implicite conversions.

WHERE To_Number(SubStr(BATCH_ID, 19, 2)) - To_Number(SubStr(BATCH_ID, 9, 2)) > 1

You can use SUBSTR to find the characters at those positions and then subtract (implicitly converting them to numbers):

SELECT *
FROM   table_name
WHERE  ABS(SUBSTR(batch_id, 20, 1) - SUBSTR(batch_id, 10, 1)) > 1;

Which, for the sample data:

CREATE TABLE table_name (EQUIPMENT_ID, BATCH_ID) AS
SELECT 'Dispense', '1000731655_000731656' FROM DUAL UNION ALL
SELECT 'Dispense', '1000746832_000746833' FROM DUAL UNION ALL
SELECT 'Dispense', '1000731637_000731639' FROM DUAL UNION ALL
SELECT 'Dispense', '1000575235_000575236' FROM DUAL UNION ALL
SELECT 'Dispense', '1000575239_000575240' FROM DUAL;

Outputs:

Or, if you want to use all 6 digits then:

SELECT *
FROM   table_name
WHERE  ABS(SUBSTR(batch_id, 15, 6) - SUBSTR(batch_id, 5, 6)) > 1;

Which outputs:

fiddle

In xase that the numabers are not fixed length you can try

CREATE TABLE batch
    ("EQUIPMENT_ID" varchar2(8), "BATCH_ID" varchar2(20))
;

INSERT ALL 
    INTO batch ("EQUIPMENT_ID", "BATCH_ID")
         VALUES ('Dispense', '1000731655_000731656')
    INTO batch ("EQUIPMENT_ID", "BATCH_ID")
         VALUES ('Dispense', '1000746832_000746833')
    INTO batch ("EQUIPMENT_ID", "BATCH_ID")
         VALUES ('Dispense', '1000731637_000731639')
    INTO batch ("EQUIPMENT_ID", "BATCH_ID")
         VALUES ('Dispense', '1000575235_000575236')
SELECT * FROM dual

4 rows affected

SELECT * FROM batch t
  WHERE To_Number(SUBSTR(SUBSTR(t."BATCH_ID", INSTR(t."BATCH_ID", '_')+1),-1)) 
   - To_Number(SUBSTR(SUBSTR(t."BATCH_ID", 1, INSTR(t."BATCH_ID", '_')-1),-1)) 
         > 1 
  

fiddle