read Sheldon - http://www.sheldonbrown.com/frame-sizing.html. If the bike has a sloping top tube then it wouldn't be unusual for the measurements to differ like this.
@yorkiefix started
London Fixed Gear and Single-Speed is a community of predominantly fixed gear and single-speed cyclists in and around London, UK.
This site is supported almost exclusively by donations. Please consider donating a small amount regularly.
read Sheldon - http://www.sheldonbrown.com/frame-sizing.html. If the bike has a sloping top tube then it wouldn't be unusual for the measurements to differ like this.