According to Cisco's documentation:

"The MAC address tables on all stack members are synchronized. At any given time, each stack member has the same copy of the address tables for each VLAN."

However, when logged into the switch I see the following:

ny-swstack01#show mac ad | inc Total
Total Mac Addresses for this criterion: 222
ny-swstack01#ses 2

ny-swstack01-2#show mac ad | inc Total
Total Mac Addresses for this criterion: 229
ny-swstack01-2#exit

ny-swstack01#ses 3

ny-swstack01-3#show mac ad | inc Total
Total Mac Addresses for this criterion: 229
ny-swstack01-3#exit

ny-swstack01#ses 4

ny-swstack01-4#show mac ad | inc Total
Total Mac Addresses for this criterion: 235
ny-swstack01-4#exit

ny-swstack01#show mac ad | inc Total
Total Mac Addresses for this criterion: 222

Going back and forth this isn't just because it is changing over time either, within certain sessions there are entries that I don't seen from the master session. We are currently waiting to hear back on CIsco from this, but has anyone run into this before? I stumbled upon this when looking into Unicast flooding, one of the hosts that is a destination MAC of flooding has a MAC entry that appears in session 3, but nowhere else.

Also, I checked an all sessions show the same aging time.