2 MAC address with seam IP

RouterOS Beginner Basics
1

Dear all
How do I prove the MAC address so that it never changes in Mikrotik? because when you open winbox you will see something like
DC:2C:6E:28:D8:C3
DC:2C:6E:28:D8:C8

with seam IP address

with regards

hEX PoE RB960PGS as switch
2

In the bridge configuration, copy the MAC address you want to use to the Admin MAC Address field.
(normally you would use the MAC address of the first port in the bridge)