Is 5lb really small for an 8 month kitten?

Forgive me if this is a stupid question - my two cats are the first pets I've had as an adult. I have an 8 month old Abyssinian-mix named Zara who seems very small. Not thin - you can't see her ribs or anything, in fact she has a little belly. She is feisty, energetic and rules my adult tom with an iron paw in a velvet glove. But when my other cat was 7 months I'm sure he was around 7lb. I got on the scale holding her yesterday and she's just 5lb. Anyone else had such a tiny cat, and was he or she well?