help with question

hello, your lectures are so useful + the notes thank you so much! i was practicing questions from a revision kit but wasn't entirely sure and need a reasoning or explanation of why we add these back on to the current amount of petty cash in hand? it says the petty cash in hand £66, and then there were the following petty cash vouchers: sundry purchases £22, loan to sales manager £10, purchase of staff drinks £19 and sundry sales receipts £47.. and it asks what the imprest amount is, I understand that the first 3 items need to be added on to maintain the float as they were taken out to be spent for those reasons from the £66 but i don't understand the last one sundry sales receipts and why that needs to be taken away