AC1900/EX6400 Virtual Mac Address Creation

Recently installed new Netgear ex6400  extender in wifi network using Netgear r6300v2 router with mac filtering. All seems to be working now after adding the two virtual addresses created by the ex6400/ac1900 to the router. Here's what happens  as far as I can tell.

The macs for extender are 9c:aa:bb:cc:dd:0e and 9c:aa:bb:cc:dd:0f.

When a device attaches via extender it shows up in router as mac a2:aa:bb:cc:dd:0e or a2:aa:bb:cc:dd:0f with associated ipaddr.

Looks like the leftmost hex digit+6 is changed as the virtual mac for attached devices (9c+6=a2).

Have had up to four devices attached to extender simultaneously and they all show up with identical virtual macs with different ipaddr in router.

I have seen 02:0f:b5 show up in other posts for 7000, 6100, or 6200 extenders but not for 6400.

Does any one know whether this mac creation happens as a function of hardware or firmware and is it repeatable? Anyone with a ex6400 seen anything different?