He's not saying he's earning the ability to "grant level" from leveling up a character with grants from another...

He's saying something like this (in a simpler perspective).

Char1: Lvl 40 and 99%
Char2: Lvl 39 and 99%
Char3: Lvl 39 and 99%
...all with previous levels earned and grantable.

Char1 grants a lvl to Char2.

Char1: 40 99%
Char2: 40 99%
Char3: 39 99%

Char2 kills a few mobs, levels up.

Char1: 40 99%
Char2: 41 00%
Char3: 39 99%

Char2 grants 2 levels to Char3.

Char1: 40 99%
Char2: 41 00%
Char3: 41 99%

Group kills a few mobs.

Char1: 41 00%
Char2: 41 00%
Char3: 42 00%


Remember that Plinko game on Price is Right or a slinky going down somestairs? Now imagine a grant a lvl going down the stairs instead.