Trail classification on the network

I've been wondering for a while and to date didn't managed to work out what the initial numbers mean preceding the distance declarations on the network (i.e. the "Global riders network" sites.)

E.g.

what is the first "5" stand for in 5 for 15km (76%) etc
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here's a complete example (Winmalee)

Firetrail:
5 for 15km (76%)
Mixed:
1 for 3.7km (19%)
Single Track - Enclosed:
1 for 0.9km (5%)

thx