Change dimensions of grid

Hi, I’m new to Grasshopper and karamba, I downloaded this file from Karamba’s page but it has no information or tutorial. I need to change grid boundary from 20 x 20 to 100 x 15 metres. How do I do it? Please help.
Ps- I know its a primitive q but I’ve only started; any help would be great.
from scratch (27.5 KB)