Really?

I was filling up my beloved automobile with gas the other day, and staring me in the face was this sign on the gas pump.

How would one go about pre-paying in advance? Isn't it good enough to just pre-pay, or pay in advance?

Apparently someone else had the same question as I did, because they tried to use a sharpie to cross out "Pre".

Now, I am not an English major, so if this is in someway correct, I hope that someone can enlighten me.