The owners manual explains this. (RTFM)
These are indicators of engine wear condition
15 at hot idle is normal, nothing to worry about
7 at hot idle is time for bearings. engine overhaul.

Oil system and coolant system monitoring are there for a reason.

It is possible to have good compression and running and weak oil pressure.

I had a catastrophic failure on an 220SE M127.
wiped out the rear cam bearing and a rod bearing.
Sudden engine death.

pay attention or pay the engine overhaul man.