You know, if you were just joking, then you should have just let it go. Now you look like you're grasping at straws to justify what you said, since any (reasonably-educated) native English speaker will be familiar with the definition of 'fraction' that he was using.
Sarten-X is 100% correct — and his original post was hilarious in my opinion. Fractions do not need to be less than 1 (or greater than -1, for that matter). Common English definitions are irrelevant here; this is a mathematical definition.