Setting an additve on an AnimSingleNodeInstance is not allowed

In editor, as soon as I hover over my newly created AimOffset, the editor spams the following warning:
" Setting an additve animation (TP_Rifle_standHip_AimOffset) on an AnimSingleNodeInstance is not allowed. This will not function correctly in cooked builds! "
I’m desperately trying to figure out what this warning means but there’s little to no information about it online.

Does anybody know what I’m doing wrong here?


Wow! There is 1 person with the problem.
I do not know how to solve it.
In fact, this engine error.
I asked a question on ansvers.