Is it normal that data I filtered out gets pulled in?

Approximate table to show you with made-up dates and amounts:

So my job is to run a total of health and dental claims our employees incurred after they were supposed to be terminated (but we forgot to terminate them). So for example, John Doe is terminated January 1, 2026, and so the report I run pulls up all the claims he incurred until today. Claims incurred prior to his termination date doesn't matter, he was entitled to use them. So I filter them out.

What I've been doing so far is using the filter function to exclude any Service Date from prior to January 1, 2026 (they then disappear from the table), and then I do =SUM and highlight the "Paid Amounts" column. I thought I was doing things right all this time.

I got audited for my work today and I was told my numbers were wrong. I then found out that it has been for some reason pulling in the numbers I've been filtering out??? I was so confused why this was happening.

From my example table above - I was expecting to see only $3 since he only incurred 3 claims after Jan 1 2026, but instead I see $5. What am I doing wrong?

My example table is obviously very easy to see that something is wrong, but I haven't been noticing any issues since the reports are usually very very long with all sorts of claims and dollar amounts. I wouldn't have questioned that I wasn't doing anything wrong until I got audited today.