Fewer!

I'm all for reusing and recycling, and bought this bag several years ago and use it all the time. I have to say though, hopeless grammar pedant that I am, I never display it message-side out, because it annoys me so much that it says "one bag less" instead of the (correct) "one bag fewer"!

Backblipped; for some reason yesterday my laptop refused to download photos from my phone despite several attempts.