Hypothetical Enchantment

every time a creature you control gets a +1/+1 counter, discard a card or lose one life.

Nonexistent Sorcery

Put two +1/+1 counters on target creature.

Would Hypothetical Enchantment's effect trigger once or twice?

Is either of Rock Hydra's abilities any different? If it comes in to play with counters, does it trigger once or once for each counter? When paying MMMMMM the next turn to grow two more heads, does it go off once or twice?

Please feel free to replace the hypothetical cards with actual cards, and also this comment if no hypotheticals remain.