It depends on what you're calling "Post deductions".
AGI is line 11 of form 1040, not line 15.
Line 11 is The Modified AGI (MAGI) for eligibility for the LLC, for most people. But if you’re filing Form
2555 or 4563, or you’re excluding income from Puerto Rico, see Pub. 970 for the amount instead .
The income phase out calculation, for the LLC, is shown in Part I of form 8863. https://www.irs.gov/pub/irs-pdf/f8863.pdf