1/4 tank in 20 gal. tank is 5 gals. Most fuel tank senders are not spot on accurate when getting low. I would fill the tank and see how much fuel was left in the tank when you put it back on the trailer. That will tell the story.
I made 2 or 3 trips to the lake with mine at or below a 1/8. I wanted to see how low it would go before I ran out. Boat was new to me and not sure about the gauge. I never did run it out. I got tired of carrying a gas can with me. In my Ranger I could pretty much predict by the gauge when I needed to switch tanks but it would run for quite a while on E.