ASUS Router integration (asuswrt) What is this connected device count?

I fairly recently bought one of the ASUS routers. I liked it so much that I bought a second on Black Friday and set it up as a wireless extender connected via cabled backhaul (which works super well in case you’re wondering) and put it up in the loft (aka Attic). Naturally, I was then really interested in the Home Assistant integration for these routers. It’s got a lot on it and I’m busy building graphs with the data - lovely stuff!

I can not figure out what the Connected Devices sensor is trying to tell me. I’ve graphed it here for the two routers.
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And here is the connected devices that the router is telling me, screen shot taken in the same moment. The numbers are quite different!
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Now, I get that 23 + 9 = 32, and I’m ready to understand that the main router is reporting all devices.

But where on earth do 24 devices connected to the extender come from?