Confusing Device Limits

Hello,

i am confused about the device Limits. Maybe my understanding is wrong.

FAQ says CC2531 firmware supports 20 devices connected directly to the coordinator, and the router has a limit of 21 devices.

So, in my calculation, if i have 1 coordinator and 2 routers, the devicelimit should be 60 (20-2+21+21). In the example in the same FAQ they are writing for the Coordinator a limit of 13 (15-2). Why is the number 15 and not 20?

Thanks!

I’d also like an answer to this question. Is the limit in the CC2531 firmware for directly connected devices 15 or 20? I see different answers in different places. I need to know, because I’ve reached 15 and want to add another.