You should read the IRS instructions for filling out the 8962.
Seems the law mentions a clawback of up to $300 per person or $600 per family if under 100% FPL.
However the IRS form basically says to treat you as if you made 100%.
Page 7, under "Line 6"
I tell clients I am not a tax person and they need to take this form to their tax prep person and ask those questions.
I personally haven't had an issue for people who make under what 100% when their estimate was above 100%.
The BIG issue is when they make over 400%. That's painful. Even more so when they are older and make $1 over 400%...that's sad.
Had one guy get an inheritance from an aunt (40k). It cost him $13k in paying back his subsidy. He wasn't very happy.