Help!

It'a my last day in Tokyo (leaving tomorrow, too 
early to do much of anything) and I have two full 
stamp cards from Anime World Star...and I have no 
idea what I can do with them!

I tried to ask the guy at the counter but 
evidently his English was worse than my Japanese 
(which is terrible! ~_^;) and the best he could 
think to do was write "3500 yen" on a piece of 
paper.  I tried to mime paying for 3500 yen worth 
of cels with it but he didn't seem to agree 
(maybe took me too literally; I did pick up the 
cels I was then buying as an example) so I am not 
sure how to use the cards.  Anyone know?

I hate to think of leaving with something 
potentially valuable unused--especially if it 
means more cels!

I also can't access my email here so will only be 
able to read email replies when I get home 
(Houston, TX), so posting here would be 
appreciated.

Thanks!
Quat(s)