Groot: How does Groot’s Flora Colossus ability work if he takes more damage than he has growth counters?

Groot’s Flora Colossus ability will do as much damage as it can. So for instance, if Groot has three growth counters but takes five damage, three growth counters will be removed from Groot, preventing three of that damage. The remaining two damage will then be dealt to Groot’s hit points.

-Galaxy’s Most Wanted rulebook