I granted almost all of them at the end.
But I initially granted some after the first team had leveled.

There is the cap, on what a given toon can grant...
You log that toon in, and it gives as many levels as it can, each time to a recipient toon who is lower level than the granting toon.
Then you log another toon in, and they can also grant levels.

It is essentially one level 80, for every two toons who were boosted/leveled from 1st to 80th.
I believe it is 39 levels each.
Which means, level your toon (who is being granted levels) to 2nd or 3rd, but be as close to 99% into their level as possible.
Because when you're done granting, and they're 80th... they'll be the same percentage through 80th as they were through the pre-granted level.