Ok, now some of you may laugh, but the first time this happened to me, I was perplexed (for a short period) :-)

I bought some used blades, got a great deal! Went to try one on the Mill, and it dawned on me the teeth were going the opposite direction that my Mill ran.

For those of you who may come across this issue, just roll the blade (inside out) and the teeth will be going the alternate direction. :-)

Waldo