Can you put multiple +1/+1 counters on a creature with a single proliferate trigger?

Proliferate lets you choose any number of players and/or permanents that already have at least one counter on them, then add one counter of a kind that permanent already has. This is defined in CR 701.27: "choose any number of players and/or permanents that have a counter, then give each one additional counter of a kind it already has."

The key phrase is "one additional counter" — each chosen permanent gets exactly one more counter of one chosen type per proliferate event. So if a creature has a +1/+1 counter, a single proliferate trigger makes it get one more +1/+1 counter, going from 1 to 2 total. It does not multiply or add multiple counters in one shot.

To add multiple +1/+1 counters with proliferate you would need multiple proliferate triggers or instances — for example, if you control two effects that each say "proliferate," you resolve each separately, and each can target the same creature to give it one counter per trigger.

Example: Your creature has one +1/+1 counter on it. You cast Contentious Plan (proliferate once). You choose that creature. It receives exactly one +1/+1 counter, ending up with two total. You cannot choose to give it two or three counters from this single proliferate.

Note: If a creature somehow has both a +1/+1 counter and a -1/-1 counter, proliferate lets you add one of either kind — but still only one counter per proliferate event per permanent (CR 701.27a).