This is the best way to calculate if a company does overnights (mainly because you get untaxed per diem). Get the hrs and multiply it times the rate of pay. I would start of with the min guarantee. Usually your first year that's what you'll make unless you're very lucky and can get a line (not unheard of, happened to me). But on reserve the company handles your schedule so they will try to make everyone fly around the same and the min. Why? Because let's say Mary and Susie are reserve at a company that guarantees 70 hrs and the company makes Mary fly 100 hrs a month and Susie just 10. Mary will now make her 70+30 while Susie will get 70 so the company just dished out 170 hrs of pay for just 110 of flying. That's why they will try to keep everyone around min. Yes they may fly you more but just prepare for the worse.
Anyhow back to the amount. When you multiply the hrs times rate of pay that will be your take home. It will just vary by maybe $100-200 at most and it's generally in your favor. Hope this helps :)