20buy ins for NL. In other words, once you have 20 buyins for $50nl ($1000) you can play any amount of 50nl tables (20 if you want)
I cant see much problem with this.

In limit, you need 300bbs for a level. So if you have $150, you have 300bbs for 0.25/0.50 and you can play as many tables of that game as you want.
It doesnt mean you can play 1/2 as then you only effectivly have 75bbs for 1/2 games.