Interaction with printed stats and token/equipment with stat reduction
It becomes 2/2.



The ability in question is


  Target creature gets -4/-4 until end of turn.


To determine a creature's power and toughness:


Start with the printed value (or the value with which a token was created).
Apply power- and toughness-setting effects (e.g Turn to Frog) in the order they were created.
Apply power- and toughness-modifying effects (e.g the ability and the counters mentioned above).


The result is the power and toughness of the creature.