In English speaking countries cycle gearing is usually measured in inches and comes from the olden days of penny-farthings. A larger number means the gear is harder to push, and a smaller number means the gear is easier to push.

Measurement = Number of teeth on chainring x diameter back wheel  
  No. teeth on sprocket

Note: These gear restrictions apply to riders in all events irrespective of the gearing used by riders from other categories in the same event.