I suggest that Strava have a page/place where we can see all our efforts for those distances:
5km; 10km; 15km; 21km; 42km (running)
20km; 50km; 100km; 150km; 200km (cycling)
When we run 15km in a good pace, for example, strava shows that is our best 15k mark, or 2nd or 3rd.
But when we runk 15km in a slow pace we do not know whick position that mark is.