Effectivity S & M?

[vk2him]

Hello, 
What do Effectivity S and Effectivity M represent?
I know effective L represent the number of received signals used to calculate strike position with distance of up to 5000km.

In truth, we don't know

If you sort by S or M the description changes:

(Effectivity S = Number of received Signals of the last hour that have been used in calculations of strike positions with a distance up to 50 km (absolute/relative))
(Effectivity M = Number of received Signals of the last hour that have been used in calculations of strike positions with a distance up to 500 km (absolute/relative))
(Effectivity L = Number of received Signals of the last hour that have been used in calculations of strike positions with a distance up to 5000 km (absolute/relative))