Hello and welcome to HealingWell.
I suspect they are giving you an estimated recovery time for him due to his extended heart disease which was discovered during surgery plus the other concurrent medical problems he has.
I am sure there is a social worker or a case manager assigned to your father so do try to find out who that person is and be sure to advocate for both you and your father by learning the recovery plan.
Healing is a personal process. I have read that recovery is all over the map, from 6-8 weeks to up to 18 months from some people.
Again a warm welcome.