What you're seeing is how mac addresses for different BSSIDs are derived within the Access Point. All are valid.
You AP in this case has a wired enet0 mac address of 9c:1c:12:cd:42:64, which is used to derive the different radio and then BSSID addresses. 9c:1c:12 is the vendor OUI, and will be consistent across the derivations. the last three octets of the ethernet mac are then shifted to derive the radio mac addresses. The first address, 54:26:40 (taken from cd:42:64) goes to the first radio (typically 2.4 GHz). The last octet is increased by 15 to 54:26:50 and is assigned to the second radio. These (54:26:40 and 54:26:50) are the base radio mac addresses, and are used to derive the BSSIDs for the different WLANs that are configured.
Your client shows that it is associated with 54:26:42 ... so it is connected to the 2.4 GHz radio (54:26:40) and is on the third WLAN (or SSID) configured on that radio. The first SSID on the radio uses 54:26:40, the second uses 54:26:41, the third uses 54:26:42, etc. If the AP supports 16 SSIDs and all 16 were configured on the 2.4 GHz radio, the last BSSID would be 54:26:4f.
So for your attachments: device.jpg shows the actual BSSID that the device is associated to. snip1.jpg is Airwave showing with AP the client device is associated to (as identified by the enet0 mac address), but not the specific radio. Snip2.jpg is Airwave showing the specific radio mac address the client device is associated to, but not the specific BSSID.
HTH