1. This looks like a bug, the reports uses a string comparison sort method which is failing due to the date format.
2. Hard to tell what the problem is from the totals, I’d suggest checking the details to see which rows are different. The reports won’t necessarily match as one filters by the invoice date whereas the other uses the payment date.
I know you’re in a major overhaul on IN, but an old issue is still without a fix. I have posted an issue about date filter not working correctly on Reports due to date format (fr-CA in my case).
Do you have any plan fixing this issue in v4 or in newer v2 ?