Advice on PSW (Post-Study Work) visa

I was looking for some advice. For PSW, although I have never crossed 20 hours per week. There were a couple of discrepancies where they recorded fewer hours in a month and adjusted them in the next month. I have got the email chain of me notifying them about this issue. Due to this, in that month, then I crossed 80 hours a month. However across my total time working, that limit hasn't been crossed. Would this be a problem for PSW, like should I get a letter of confirmation from them that this was their mistake?