It doesn't really have any connotations for me in this context. Obviously, if it were to do with investments, 'bubble' would be an odd choice. In the context of invoices I don't think it really means anything.
Agreed, I thought this would be a cool css / js tooltip effect or something.
I thought it would be some article about the difference between cash and accrual accounting, and how temporary differences in these numbers can cause (short-term, but potentially fatal) problems.
:) sorry to disappoint! sounds like a good idea for an article.
I'm not sure I'm disappointed, really; just slightly surprised.