Increase the number of dwarves you embark with.
You must use this tool before embarking (e.g. at the site selection screen or any time before) to change the number of dwarves you embark with from the default of 7.
Note that the game requires that you embark with no fewer than 7 dwarves, so this tool can only increase the starting dwarf count, not decrease it.
Start with a few more warm bodies to help you get started.
Start with a teeming army of dwarves (leading to immediate food shortage and FPS issues).