Can anyone tell me how much fuel each tick mark measures on the fuel gauge on a 2002 Suburban with a 32 gallon tank?

How many tick marks are there?

uh, each 1/4 mark is 8 gallons? do i win something?

or are you asking for real world experience? the first half of my tank is bigger but i have no idea how much.

there are 3 gallons left when the light goes off, i haven't verified it though.

Kind of where I was heading with that!
Most mfg's leave an idiot factor of 8% from when the low fuel light first comes on. In a 32 Gal tank that'd give you just over 2.5 gallons.
Every GM I've ever owned seemed to take forever to go from F to 1/2 and then was mucher quicker falling from 1/2 to E on the gauge.