Does anyone know how or what the OSD signal % means?

I am using the current release of Mythbuntu (7.10) with a Leadtek DTV2000H card receiving Free to Air DVB-T ( all VHF freq ) in Sydney, Australia

Last night I was playing around with the antenna system which has a masthead amp and got the following readings

1) Lead direct to wall ***Signal 50% - S/N 4.8 db - BE 0 - Lock OK
2) 10db attenuation ***Signal 55% - S/N 4.8db - BE 0 Lock OK
3) 20bd attenuation *** Signal 60% - S/N 4.8db - BE 0 Lock OK
4) 2 way splitter *** Signal 75% - S/N 4.8db - BE 0 Lock OK
5) 3 way splitter *** Signal 100% - S/N 4.8db - BE 0 No Lock
6) 4 way splitter/Amp +12db *** Signal 35% - S/N 4.8db - BE 0 Lock OK 
7) 2 piggy backed splitter/amps ***Signal 20% - S/N 4.8db - BE 1000 No Lock