No any Value Of Signal Strength on 0% Quality, Quality is to important in Stb, Stb Can't display Any pictures if No quality , in case of full signal with Low quality >20 Pictures Run As Scratchable CD in some case if quality is 0 stb can't read channels name.
Signal strength is how strong the signal you are picking up is. The closer you are to a transmitter the more signal you will pick up with the same aerial. Further away and the signal level will drop and you will need a larger more powerful aerial and/or amplification to get the signal level back up.
Signal quality is how good the information you are recieving actually is. If the the signal is suffering due to reflections/ghosting or interfernce from electrical installations switches/motors etc then the quality will be poor as these problems will cause the loss of data in the signal as the effect of them will block/overpower the signal and your box won't be able to "read" the true data. Without any of these problems the your quality will be high.