HELP BH10 & RSSI

I need help…
I have a BH10 in 5.7 GHz, to 20 miles, they are configured as Master and Slave.
Of the side Slave has a RSSI of - 70 dBm, when I notice the side Master (from the Slave “AP Eval Data”) it indicates me -84 dbm. Because it can be?
The link this working with LOS, but I have courts.
At the moment I have connections to 24 miles that don’t have any problem, with a RSSI in both sides of approximately -74 dBm.