How to calculate Net Income for Adult/Child Dependant Grant

pingu-lingo

I have been looking at the SLC Factsheet for calculating Adult and Child Grant Dependant Grants (sorry I cant post a link as im a new user)

In their calculation it gives a breakdown of how to work out what you are entitled to, and uses "total net income" in its figures.

Does anyone know how they calculate this total net income?
Is it Net pay + tax credits - allowable expenses?
or is tax credits not included? And what about child benefit?

Factsheet says;
"total net income - disregard figure = residual income"

Many thanks