Bagels and Pate Fermentee question.

Hey there everybody,

I've made Jefferery Hamelman's bagels many many many times  with great success.  But, yesterday, for the the first time I noticed that at the bottom of his recipe in Bread it reads, "note: 20% of the overall flour can be pre fermented in a pate fermentee".  I can't exactly figure out why this confuses me so much.  I've never baked with pate fermentee, only poolishes.  I guess my questions are...

Would I make a 20% scaled down version of the recipe and then add that to the dough next time I made bagels?  And then reserve about 20% of the full recipe once finished?

Really, if someone couple explain this to me like I'm 5 years old that would be great.

Thanks a bunch everybody.