Your compensation is the amount in box 1 of your W-2 minus any amount in box 11. Nothing on the Schedule K-1 (Form 1120-S) is compensation.
The reference you provided is not a reference that defines compensation. It references Modified AGI for determining whether or not your income (not just compensation) is too high to make the contribution. The definition of compensation is in IRS Pub 590-A:
https://www.irs.gov/publications/p590a#en_US_2021_publink1000230355
