There’s no official number of devices that our AP’s can support. No vendors are able to provide this number as it’d be very difficult to produce. It is based on a number of factors like CPU, radios, memory, etc. but more importantly, the type of utilization. Video streaming vs. web browsing. Here is a good external read on Access Point loads.
With that said, the AP 55 technical specifications can be found here
Please read my response above. Like I said, there are no sizing guides for AP's because they are not based on number of users but on a variety of different factors like load/type of traffic you are expecting, types of devices connecting, etc. Have a read at the links I have attached above for further clarification.
