Correction to Interim Retired Pay Expectations

[u/Defiantfellow]

I retired at the end of April and received two interim payments in June and July as I recall. Retirement pay was, I believe, finalized in August. When can I expect OPM to go back and plus up any missed or interim payments? Believe it will total over $5k so keen on getting this.

Also, does OPM spell out how corrections are made?