What determines number of riders/your position in a segment?

During a lap/segment, the leaderboard will show my position out of a number of riders such as “200/288”.  What determines the 288?  Does it include those who have finished before I started, those who started before me, those finished before me, etc…I can’t figure it out.  I pass people (not many, for sure) but I don’t see my finish go up.

It shows the riders currently on track who completed the segment with their fastest time  I think from the last hour.

Yup, it’s the number of riders through in the previous hour.

Thanks!