Power squirrel's pet giant skill?

Check your attack range? Might be buffing you with w.att/m.att like the other bonus attack pets (3/5/7 w.att/m.att)

Without pet: 64587 max, with pet: 65203 max.
That's just the 4 atk buff you get for 1 pet it seems (beginner skill is gotten upon pet equipment that says it's 4 atk for 1 pet)