dovecot - May 2015 - Understanding the "doveadm replicator status" output

Where can I get more detailed information about the output of the 
'doveadm replicator status' ? man doveadm-replicator isn't enough.

For example, Total number of known users = 29409, but the server has 
only 17667 users. This is confusing.
Look:
# doveadm user '*' |wc -l
17667

# doveadm replicator status
Queued 'sync' requests        0
Queued 'high' requests        0
Queued 'low' requests         0
Queued 'failed' requests      0
Queued 'full resync' requests 12962
Waiting 'failed' requests     16447
Total number of known users   29409

What it means to "Queued full resync requests" ?

thanks!
Thiago Henrique