Are you allowed to use all

http://ratemyserver.net/index.php?iname=proof+Potion&page=item_db&quick=1&isearch=Search simultaneously?

its, +20% X elemental resistance, -15% Y elemental resistance, so if my math works, if you are allowed to use all:

Say, you are using High Risk Card (you are Neutral Property), you used Water Proof Potion you gained +20% Water Resist, but -15% Wind Resistance, then you used WindProof Potion so you gained 20% Wind resistance (total Wind Resistance = 5%

),... you used all Proof Potion, you gained a net of 5% resist on 4 elements.

Is my assumption correct? or it doesn't work that way?

thanks!