How is it possible for the gas gauge to work baskwords backwards

I bought it this way it works even so when it's full the empty lite is on

the fuel pump sender/float switch is bad.you would have to replace the whole fuel pump module assembly to fix it.bad to go out on the chevys!around $350.00 if you do it yourself.or just keep the tank full,and don't run it out of gas!look to the right of this page under problems for your vehicle highlighted in BLUE,and you will find it listed.