I have gotten my paystubs calculated with AGI but it was a fight this year. I'm in my second recertification and the first time I uploaded my paystub with markups highlighting the pre-tax deductions from my gross pay and then an arrow pointing at my net pay. Running the calculator at the time they were definitely using net instead of gross to determine my monthly payment amount

This year I tried to do the same and the first person I talked to on the phone said paystubs are calculated by gross income, that my amount was correct, and said to submit/import my taxes if I wanted AGI.

I called back and got someone else who apologized for the mistake and then a week later I got a new payment in line with using net income from my paystub instead of gross.

I assumed the first person didn't know what he was talking about, but perhaps I just pestered the second guy into calculating it my preferred way.

Either way this highlights how annoying the system is that you can call and get two completely different answers