"Advantages and Disadvantages" System

I've read through everything in my packet but I keep seeing a reference to advantages and disadvantages without seeing numbers or a system to define it. Is this open ended for the DM to make up or did I miss a page somewhere?
I'm sure it's in there somewhere.

For reference, until you find it, advantage and disadvantage work as follows:

Instead of rolling a d20 for the check like normal, roll 2d20.  If you have advantage, only look look at the higher die roll (and ignore the lower roll); if you have disadvantage, only look at the lower die roll (and ignore the higher one).  

If you have advantage from multiple sources, only one of them counts.  If you have disadvantage from multiple sources, only one of them counts.  If you have at least one source of advantage and one source of disadvantage, just roll the 1d20 like normal.

The metagame is not the game.

FYI advantage/disadvantage can be found on page 2 of the How To Play PDF.

Yan
Montréal, Canada
@Plaguescarred on twitter

Yup found it, I guess reading D&D rules at 4 am and drinking doesnt quite work out... lol Wink
nope. But shows your admirable dedication!