I am looking for some clarification on the card Gleam of Authority. The wording on the card is

Enchantment - Aura

Enchant Creature

Enchanted creature gets +1/+1 for each +1/+1 counter on other creatures you control.

There is also a tap ability to bolster and vigilance. My question is on the enchanted creature get +1/+1 for each +1/+1 counter on other creatures you control. Is this text a one time application?

For example, if I have 3 +1/+1 counters, my enchanted creature gets +3/+3. If I add another +1/+1 counter to the board later, will the enchanted creature now have +4/+4 or will it remain +3/+3?

Thanks!