Is this a bug?

in this game [game;id:1654147;move:9] I was checking if the * can be a 0, while 0's is not in the set of medium game, and for my surprise, the site accepted it, I think this is a bug, or did I miss something here??

My opponent Karl asked, if it can accept the 0 does it accept 10 too??

I had the chance to try * to replace 10 in other game, but it did not work, then it only can replace 0 in the medium game which 0 is not one of its tiles set.

zero (0) was accepted?really..I did not think thetre was a .gif for zero,oh I see it was used as a wild tile.then is ten possible?I will watch for an answer here.

I looks as though Nagy Fathy already tried that and couldn't use the * as a 10.

Zero is a single digit, so it can be used. 10 is two digits, so it cannot.