I got my commander returned to hand. The game passed priority to attack and after that ended turn. I had 3 Mana available. Next turn I could cast it for two Mana. It looks like the check was for 4 Mana as a t would be increased if it would be returned to commander zone.
On yet next turn it passed priority when I had 3 Mana and another two Mana creature on hand. It looked like also checks for all other cards in my hand was increased by 2