If you need a confirmative answer, please reach out to Aruba support or ask the question via your local Aruba Sales team.
I have always read the number of users as the number of users, not the number of IP addresses. There is information out that there is a limit on 2 IPv4 and 4 IPv6 addresses and I see in my environment regularly that the privacy IPv6 IPs are rotated and it stays at the max of 4 active IPv6.
Also, found this command that suggests something similar:
(md7010) #show user-table station
Flags: 0x01 - RadAcct, 0x02 - UDR, 0x04 - MacAuth, 0x08 - 802.1x Auth
0x10 - OnCall, 0x20 - L2Mob, 0x40 - xSec user, 0x80 - RAP Bridge
0x100 - Rad InterimAcct, 0x200 - L3listSortedV4, 0x400 - L3listSortedV6
0x800 - ACR or SuiteB user
Station Table
-------------
MAC BSSID IP Type Flags AAA Prof
------------ ----- ----- ---- ----- --------
34:ea:34:xx:xx:xx ac:a3:1e:xx:xx:xx 1(1) wireless 50d WLAN_PSK
98:fe:94:xx:xx:xx ac:a3:1e:xx:xx:xx 5(5) wireless 109 WLAN_WPA2-aaa_prof
84:b8:b8:xx:xx:xx ac:a3:1e:xx:xx:xx 5(5) wireless 50d WLAN_PSK
a4:38:cc:xx:xx:xx 70:3a:0e:xx:xx:xx 1(1) wireless 50d WLAN_PSK
d4:f5:47:xx:xx:xx ac:a3:1e:xx:xx:xx 5(5) wireless 10d WLAN_PSK
8c:85:90:xx:xx:xx ac:a3:1e:xx:xx:xx 5(5) wireless 509 WLAN_WPA2-aaa_prof
5c:f5:da:xx:xx:xx ac:a3:1e:xx:xx:xx 3(3) wireless 509 WLAN_WPA2-aaa_prof
I've not seen issues in IPv6 environments with customers hitting the user limit, and I would expect issues to be widely spread if the number of IPs was counted instead of associations.
Others may have more information or check with your local SE or Aruba Support.