Masternode rewards are half the block reward. If it's a POW block you will get 100 MAG, but if it's a POS block you get small amount since staking doesn't reward much yet (only 2+ million in circulation).
The number of payouts should be even between POW and POS, although sometimes I get unlucky and have all payouts as POS. And sometimes lucky and get most of the payouts as POW So just let it run longer and you'll see better results.