Continent Sculpting
These settings will change the way actual landmasses generate. You can adjust any individual value by pressing up or down on your keyboard or by entering a value.
You can also randomly change the settings by entering a number in the "distribute units" field (or keeping the default 16) and then clicking the "⟱" button. This will then randomly distribute that number throughout all the different fields and automatically re-submit the form.
How continent sculpting works in general
The first two rounds of generation create a bunch of green tiles in a sea of blue tiles. These tend to already be clustered in some areas and empty in other areas.
The continent sculpting settings then come into play and connect these green tiles together in the directions and amounts given.
For example with these settings, "Sculpt bottom" is set to 4, so green tiles that are 4 units away from other green tiles will be connected together by a kind of "bridge". Meanwhile, "Sculpt bottom left" is set to 2, so you can see many instances where a green tile will connect to another green tile 2 spaces away.
Each round builds upon the previous rounds, so bridges that have been generated can then be connected to other parts of the terrain.
Eventually, you'll get more of a finished product.
After some cleaning and the rest of the generation settings, you get a final product.
You can see these kinds of changes for yourself by Disabling everything from "Fill Continents" down (press "v" on Fill Continents).