I’m not too familiar with those parameters, but the process is always the same :
T200 is started by equipment X when it sends a message AAA to equipment Y.
As long as the ack from Y is not received, T200 is running.
If no ACK is received after expiry of T200, then X will repeat the message AAA one more time and restart T200. This process can be repeated up to N200 times, if no ACK is received.
If ack is received, then T200 is stopped, and will be restarted when another AAA is sent from X to Y.
Beware that there are many T200 and N200 (one for the BSC, one for the BTS, one for the GSL, etc…)