For example, if I said "I will send the report over on Wednesday, if not before"
YABU - I won't send it before Wednesday
YANBU - I might send it before Wednesday
For me, it's "if I don't send it before Wednesday then I'll send it on Wednesday" (YANBU) but I'm pretty sure my colleagues think it means that I'm suggesting they won't accept the report before Wednesday (therefore YABU). I just don't want to rush through the bloody report 😆