Inverted Dish

I followed the good article on offset dish angle  https://www.satsig.net/22-deg-offset-dish.htm
I understand that:  Inclinometer angle = offset angle - calculated sat el angle. ( zero up for inclinometer). I used my iphone to check some already installed dish with clinonometer a free app. It proves good.
But what is the inclinometer reading for an inverted dish, suppose I hold inclinometer the same way?
I check a prodelin 3.8 m inverted ( sat el angle = 4.9). I get 25 deg ( zero up/down). I cannot figure out how it came to 25 (or 65 deg the other way). Thanks