It's a bit tricky to understand, and to explain. But, if you don't understand it, you think it's just a way of ensuring that you get more R districts.
IMO, it's important to know how it can backfire if you underestimate the number of R voters you need to add to the D districts to flip them.
Anyhow, I hope that one result of this election is that more places go with laws to ensure gerrymandering can't happen. It's absolutely bullshit that parties get to draw districts to pick the voters they want. There are some places (Minnesota?) that have non-partisan commissions that draw the maps. That's how it should be done.