acua subscribe gives a subscription to a user. See acua addRec for a description of the arguments. After a user is unsubscribed (by acua expire), the account will be restored to its state before the subscription (i.e. same limits as before). This also means that any changes done with acua modRec will be undone when the user is unsubscribed.
Example: acua subscribe foo 90d 240 120 will give user foo a subscription for 90 days, a time limit of 4 hours a day in 2 hour sessions.