1999 Oldsmobile Cutlass HELP I HAVE NO Idea WHAT TO DO

I WAS DRIVING MY SON HOME FROM MY PARENTS HOUSE AND JUST FILLED MY CAR WITH GAS YESTURDAY----UPON LEAVING THE HOUSE----MY FUEL GAVE STARTED READING THAT THE TANK WAS EMPTY ---THIER WAS NO WAY I DROVE THAT MUTCH IN A DAYI STOPPED AT A GAS STATION TO PUT IN A LITTLE FEARING IT WAS A LEAK AND THE GAGUE SHOT BACK UP TO FULL AGAIN ONLY ON 5.00 WORTH OF GAS? PLEASE HELP ME WHAT IS GOING ON W THIS CAR?