the system capacity is 3erl@2%…
it means that when 3 erlangs are sent into the system, there are 2% which will be rejected.
If you send 7 erlangs, there will be about 50% of these 7 erlang which will be rejected.
The reason is that only 7 simultaneous can be handled. And statistically, 50% of the incoming calls will arrive when all 7 TS are busy.
And other times, only 2 or 3 TS are busy.
This is all linked to the random arrival of calls.