Basically ( Not related to any manufacturer ) it's up to 254 MAC address (of associated & connected clients) per radio module per SSID per AP. (Dosent matter the AP type)
We in Aruba set default setting as 64 (Instant and controller environment ) (you can change it if you would like) - it's make more sense :) and giving excellent client experience.
I personally prefer not to pass 25 client devices per AP per SSID per radio module. (But also this is depends: site type,client needs,deployment method and more)
LAST NOTE: on instant environment each VC group can handle up to 2048 clients