When -t is used with the -a option, nnusage will list the users ordered after the total usage time. Otherwise, the output will be sorted according to user names.
Since it is possible to suspend nn, or leave the terminal while nn is active, nn tries to be intelligent when it calculates the usage time so it will truly report the actual time spent on news reading.
The nn package must have been compiled with the STATISTICS option turned on to produce the usage entries in the log file.
Only nn sessions longer than 5 minutes are registered in the log file.