What exactly is your application? Yes those numbers are correct for the unit, but there are other factors that come into play.
if SIP to PRI/analog, then your limitation is 60 TDM to IP conversions
If SBC then you are limited to 100 Simultaneous calls,
If Proxy then it depends on calls with/without VQM and transactions used.
More info can be found in the feature Matrix under voice performance:
If Proxy, then use this resource calculator tool:
It is being used as a SBC between the telco and my Cisco UCM. The Cisco PBX is handling the conversion to SCCP to the IP phones so straight SIP between the 924e and PBX.
So from the options above, I have a hard limit of 100 calls.
Yes the Hard limit MAX is 100. That number can very depending on your configuration and types of calls (transfers/forwards). Just monitor your CPU usage and Memory during peak hours to make sure the unit is not overloaded and dropping calls.
Hope that helps.