Step 3.9 - Settings -> Timed Messages Settings

Only master can use the Timed Commands (IM commands):

Yes - If set to Yes, only the master can use the Timed IM commands.
No - If set to No, both Master and operators can use the Timed commands.

Minimum time and Period:

If you want to ensure that your operators don't advertise in the groups too often, set this to the minimum allowed time.
Setting this value will ensure that an operator can't set Timed Messages timers below thi value.

A value of 30 minutes will ensure that a Timed Message can't have a timer with anything less than 30 minutes.