SBC 4500 Session Capacity displays 2,000 but only 1,000 are activated

Hello Dear All,

Need your help.

I have SBC 4500 appliance with Release S-CZ7.3.0. and we have some issue with SBC session capacity.

At the beginning we have 1,000 sessions.

we recently upgrade the session capacity from 1,000 to 2,000 sessions by adding another 1,000 sessions.

But after that We can not have sessions over 1,000. Session Capacity displays 2,000 but only 1,000 are activated.

Why we cannot use the full 2,000 session capacity ?

Here are some outputs:

#show session

#show sipd sessions

#show licence ( Two lines of session licence)