I have just completed the setup of the Archer C80 AC1900 MU-MIMO Wifi Router for my home network behind an AT&T Arris BGW210-700 modem using Passthrough Mode. 

I am not sure about one of the settings of the TP Link router - Under the Internet symbol on the admin page, MAC CLONE which is on the admin page Internet which has two settings Internet and MAC CLONE. 

Below the MAC CLONE heading there is a drop down box having "Use Default MAC Address".  Below that is a shaded box showing a MAC and is the same MAC as the TP Link label EXCEPT FOR the last two alphanumeric characters.  The TP Link label has the last two characters as B0.  The last two characters of the shaded box are B1. 

Everything seems to function properly - wifi and ethernet - all internet service seems to function properly.

Question - Is this correct and proper?

If this is correct and proper - would someone provide a short and simple answer/comment.  I just need reassurance this is okay.  I have limited knowledge of the inner workings of network "stuff".