I am new so apologies if not OK to jump in and ask something as I am in similar position in that just had a back payment and I don't know how to check it. I see you refer to a letter being sent so I will ask for that.
The follow up point is something I have asked in the forum today in a new post - as soon as I got the backpayment (and before I have even started to get to paying off my huge debts) I got a journal entry saying I had a compliance interview from an officer at another branch. I assumed this happens sort of automatically when there is a back payment for a long period of time. I won't repeat that question here.
I will ask for the letter in my journal setting out what the catch up payment covers as this is not clear. I can check the Payments tab to see what I get each month though its so ie you don't know one month to the next I may ask for confimation to be added into the letter what the run rate or usual monthly payment will be if nothing changes. That way it can be checked and I we know where we are a bit more.