HELP! Time Synchronization

I have configured my XP workstation to sync with NTP server every 30minutes
(SepcialPollInterval) . The workstation only in WORKGROUP and without any
Domain Controller.

When I added the multiple NTP server entries with COMMA separate in between,
the time will be synchronize every 17 minutes. However, if I enter multiple
NTP server entries with SPACE in between, the time will be synchronize every
30minutes as I defined. This is followed Microsoft Article ID 223184.

However, I wish to know what is goes wrong with COMMA added in the entries
and caused the time synchronize every 17minutes? Anybody know answer?

Many thanks.