Abzan Battle Priest text says: "Every creature you control with a +1/+1 counter on it gets lifelink". It is expressively written as "a" +1/+1 counter.
As some other white creature with Outcast ability (and some other cards too) Priest grants some special ability to creatures with +1+1 counters on it. But I think the text should be edited: In my opinion, it may be read as the creature has to have only ONE counter on it, while it could actually have more than one.
I believe a phrasing like this one: "...with at least one counter +1/+1 on it..." should be better.
This is true also with reference to the many other cards that present this same ambiguity: that is, they report the word "a" instead of "at least" on the text.
What do you think about it?