If you're referring to this:

Can all of these levels be granted at once?
Yes, a character can award all their grantable levels at one time.
I don't think they're talking about granting every single level you have in one mouse click. As far as I know, you can't grant more than 1 level at a time -- It's even mentioned in the API:

Regardless of the value of the levels argument, the function only grants a single level to the unit.