Spells sometimes not using reagent?

[Polluxo]

Sometimes when I shoot off a spell that uses 2 reagents, one of the reagents won't be used. Why is this? I don't have the skill that on chance uses less reagent.

[Z_E_N]

Sometimes when I shoot off a spell that uses 2 reagents, one of the reagents won't be used. Why is this? I don't have the skill that on chance uses less reagent.

I figure its related to the Reagent Conservation skill (which has ubsurd requirements at 75 Intelligence and 75 Greater Magic).

I'm guessing we always have an innate chance to use one less reagent, maybe less than 1%. This is a place holder for when we actually get the Reagent Conservation skill which will increase that chance.

I've noticed this as well though. I always go out with an even number of resin (say 50) for casting acid arrow. Every now and then I will check my bag and suddenly have an odd number (say 33).