Xert models the data differently than other platforms – by design.
Xert Only Counts Elapsed Time - Support - Xert Community Forum (xertonline.com)
Ride time v elapsed time from garmin to Xert - Support - Xert Community Forum (xertonline.com)
Laps may be coming down the road. 
Showing laps in activities - Support - Xert Community Forum (xertonline.com)