Two Different Settlement Amounts Both within Validity Date...shocking!!

So I had asked for a settlement letter on FNB personal loan on the 22nd of April 2022 which is valid until 05 May 2022. The agent advised that I should call in again before I settle to confirm the settlement amount after the debit order has cleared. Today (28 April) I called to ask for my settlement amount before I pay and guess what my settlement is R1000 more than the previous quote that is still valid and I'm told it's the interest.

What does a validity period in the settlement letter for then?