The error you're pointing out does not exist in general. % just means "per hundred". If I say A is 110% of B, I'm just saying there are 110 A for every 100 B,

The error you're pointing out does not exist in general. % just means "per hundred". If I say A is 110% of B, I'm just saying there are 110 A for every 100 B, which is perfectly reasonable in many contexts. Of course it doesn't make sense to say "Give 110 for every 100 you have available", but that's just one particular context. On the other hand, "Give 110 for every 100 you think you have available" makes perfect sense, if you interpret it to imply that people generally underestimate their ability / hold back.