Normally there is a timekeeper singing out race splits at the finish line each lap. So at 300 metres, 700 metres, 1100 metres. The finish time might be sang out or just recorded.
So working out lap splits for 6:00 mins for 1500 metres which is 4 min per kilometre pace or 1:36 per full 400 metres of track.
300 metres 1:12
700 metres 2:48
1100 metres 4:24
1500 metres 6:00
adding or subtracting 4 seconds per lap gives a 15 second overall race adjustment.
I have done quite a few in my former life time as an athletics club member.
Don't get sucked in by running someone else's race.
Once you get the hang of these, you will find out what works for you better. Going out hard or even paced or sitting and kicking.
5000 / 10000 metres on the track is hard work 12 and half laps for the 5km and 25 laps for 10km. No place to hide.