"Extraplanar geometry isn't so hard once you get used to thinking in twelve dimensions."

Zimone, Paradox Sculptor

At the beginning of combat on your turn, put a +1/+1 counter on each of up to two target creatures you control.
{G}{U}, {T}: Double the number of each kind of counter on up to two target creatures and/or artifacts you control.

Foundations

"'Impossible' is a construct born from the assumed limits of our intellectual capabilities."

To double the number of each kind of counter on a permanent, put another counter on it for each counter it already has. Effects that interact with counters being put onto permanents, such as the effect of Branching Evolution, apply as appropriate.