From a N.Y. Times article, '...to meet the FAI definition Fossett had to fly at least 12,400 miles and to remain outside an imaginary circle 4,143 miles in diameter drawn around the South Pole. Circling the earth at the equator is a distance of 24,900 miles.' Fossett flew 19,428 miles in 13.5 days.
From
www.newsmax.com, 'Fossett is the first person to fly around the world alone in a balloon. Swiss balloonist Bertrand Piccard and English co-pilot Brian Jones hold the record for the first successful (balloon) circumnavigation of Earth. They covered 25,361 miles in 15 days over the Northern Hemisphere in March 1999.'
Note that although the FAI has not approved his record, Guiness has, even though he was drinking Bud Light (yech!).