Not at all. Numbers aren't easy.
Let's take numbers out of it.
On July 5th, I give you an apple and you put it in your bag. On July 10th I give you two apples and you put those in your bag. If you look in your bag on the 5th, you have 1 apple. If you look on your bag on the 26th (today) you have 3.
If I ask how many apples you got between the 10th and today, the answer is 2. So overall you have 3 apples, but only 2 were given after the 10th.
We know overall we are looking at 3 apples. But we've broken it down into what was received before the 10th and what was received after because it's easier to count if we split into these two sections of time.
Now I know I've given you 2 apples after the 10th. But suddenly you say that after the 10th you only got received 1. So, my problem, is how come I gave you 2 after the 10th, but you are only claiming you've got 1.
That's the first issue on these banks. Your written notes show you've sent £235 to him after July 10th. But his bank only shows £206 going in. You've sent 2 apples, but according to his account he's only had 1.
Re-write/double check the amounts you think you've paid him since the 10th. Because they should equal exactly, to the penny, what his bank shows after the tenth.
Then once we've worked this step out, can we then go back and work out what's happened for the first part of the month, from the 5th to the 10th. We haven't forgotten that's when you started paying from. We're just doing a 2 step process to work the whole thing out.