Can you not just enter the decimal number as is?
I have done this with some of the linemen attributes that occupy the same slot, and they show up in-game fine.
For example, I have Lions center Dominic Raiola with:
I entered "23" (20 + 01 + 02) into my 3rd ability slot and all three attributes show up fine when I load the roster in-game.
I think the game can read it either way.