Need help with laserengraving plugin

[Jdigim]

Is there documentation on how to use the laser engraving plugin. I have a gecko 540 driver and UCCNC using Mach 3 post processor and a Jtech 7W pro laser. I experimented with 400x pixel by 400x pixel image but the machines starts to laser a larger area and all I saw was black lines, never really engrave anything that look like a photo in the 2 minutes in before abort.