2018 e-GOLF Question on 80 Percent

[CORACADEMY]

I recently purchased an E-golf and noticed that it doesn't display the battery percentage. I'm trying to figure out the 80 percent rule for estimating the remaining mileage. If the car can go 145-170 miles on a full charge, would the 80 percent rule simply be 80 percent of 145? I understand that setting up a schedule is an option, but I'm attempting to calculate the relationship between miles and battery percentage.