A quick question, just to clarify the boosting procedure... Are the "grantable levels" earned by account or toon?

I'm thinking this is obvious is you have done it already... I want to make sure I understand this completely before create my plan.

Here is what I want to clarify: We'll say you do something like A>B>C>D>E, and have L60 toons on each account. Now lets say hypothetically, you are all out of grantable levels except for account "E", which has 10 more levels to grant. Account E grants a toon on account D levels 20 to 30. At this point, account D will have 5 grantable levels, right? And can you use the L60 toon on account D to grant levels 55-60 to a toon on account C? (or is the L30 toon on account D required to be the "granter"?)

Thanks in advance for the info!