His ultimate, at rank 3, has a cooldown of 120 seconds. At maxed cooldown reduction, it has 72 second cooldown with a 2-second cooldown on a 10-second cooldown refresh. Assuming you hit both Ult and your first Recall at time 0, you can get 6 recalls by time 12 (actually 7 which is unnecessary). 12 elapsed seconds plus 60 Recalled seconds equals the cooldown of 72. Total mana cost is 500 (200 for ult, 50 per recall). Due to cooldown clipping there are only 3, not 4, possible item procs in this period (eg innervating locket).