Curious about 95 Camry fuel tank size vs. warning light

Always wondered about this:

I've read that my 95 Camry gas tank size is 18.5 gallons. When I let my tank run real low (fuel warning icon/light goes on), I always fill up within a few miles and it takes 15.5 to 16 gallons to get to full. I've never dared running longer for fear of running out of gas and damaging lines and filters.

Does anyone know how much gas is actually left when that light comes on? I know logic would be 18.5 - 15.5 = 3 gallons, but 3*27 = 81 miles seems to be a lot of safety margin when the light comes on. Thanks

Toyota low fuel warning lights are usually set to come with about 3-4 gallons remaining. Yes, when on highway, it would seem that the light would come on early, but what if you were driving in heavy stop and go traffic. The car has no way of knowing what kind of driving you're doing unless it has a trip computer, and those have a margin of error.