1, it’s everything isn’t it? Including all pot movements? I’ve just tracked back to find an easy day to calculate and I spent £37.50 on Saturday, but had £7.50 external transfer in, and £27 from a pot, so my total says £10.
2, calculate it yourself and then just paste the transactions over the top of your previous file.
Reconciling budgets is not something Monzo are going to care about or implement, regardless of how “easy” you think it might be. It’s incredibly niche. Monzo will not be “wrong” so you’ll need to work out how to make YNAB match it.
The request for a running balance in the app is now on year 7 and no sign of it