Can someone read the signal strength data from my modem?

I don't know how to interpret the signal strength data supplied by my modem. I am looking into surge protection that would include my broadband coax connection. I read from the internet (big grain of salt), that you can loose 2db(??) of signal through the surge protection device itself. I want to find out if I have more then enough signal strength to play with, to accomidate such a loss. DSL reports has a page to what the signal strength should be, http://www.dslreports.com/faq/16085. I don't know which numbers from these tables I should be comparing. (Both screenshots are the same table. I was trying to get as much of the table as possible.)