E220 RSSI Values

Hello, Frist of all, thanks for your libs :D it's too useful. I'm trying to understand the RSSI values that i get after a received message. In the E220-900T22D datasheet the Receiving sensitivity is typical -147dB, but testing it with the modules 20m far it giving me 206(positive). So if the sensitivity is -147dB i'm getting 206 and still working fine, maybe i'm setting the wrong configs. thanks.