[Igor Relja]

Not just rating, it also takes previous results in that series into consideration. First week is just rating, later championship standings + rating. So it's possible to see somebody with lower rating who has participated more in that series get pushed to server 1 at the expense of somebody with high rating, but only joining series in later weeks.

But yeah, just count the people above you when registration closes (5 minutes before the race) and you'll know in which split you are.