MAC address on Gateway does not match Fing Detection

AnimalFarm6

I have had to replace my Gateway through Xfinity twice due to being compromised. I installed Fing for Desktop and found that the Gateway I have now the MAC address does not match- it is off by one digit at the end of the address. 
I do not have a FING box yet. Can I manually set the MAC address to my modem and block the one that is using my Network? Also how can I find where the other Gateway connection is coming from? No help from Comcast.

MDavide

Hi ,
every channel has its own MAC address, so a wired connection has one , 2.4 GHz has another and 5 GHz another one again. 

Usually they differ for the last digit. 

I think this is the case, but on the label they should all be reported. 

Cheers,