A new UE4 user, need help getting clarity about royalty fee

[Galeon]

How do you know for certain that a donation button is seen by Epic as an income?

I just know that any money income related to a game is ruled by royalties.

you with 63.000 dollars and THEN you still pay 5% royalty over 87.000 dollars (and not 60.000) wich will be 4350 dollars taken from the 63.000 you had left.

You pay 5% royalties over your income that is 63.000$.

Perhaps someone at Epic can confirm that one ?