The cover fees amount is always based on the final transaction amount (not the initial amount entered).
For example, cover fees on $75 actually covers the fee for the amount of $77.55. The reason we do that is so that the user is still giving $75 to the church and rest is all the fees covered. So if we plug it into the math -
(77.55 x .029) + .3 = $2.55 (rounded on the penny)
Subtract that fee from $77.55 and you get $75 (which is intended for the church)
Now if we took the math above and applied it to $77.48 ($75 x .029 plus 30 cents), after fees, the church would only be getting $74.93 when the intention was for $75. Here's the math for that -
(77.48 x .029) + .3 = $2.55 (rounded on the penny)
Subtract that fee from $77.48 and you get $74.93 (where the user intended $75 towards the church)
See the below screenshot for a couple examples of this: