How Many Cats? - A bit silly but OK!

TEACHER: IF I GAVE YOU 2 CATS, AND ANOTHER 2 CATS AND ANOTHER 2, how many
will you have?

Johnny: Seven Sir

Teacher: No, listen carefully. If I gave you 2 cats, and another 2 cats and
another 2, how many will you have?

Johnny: Seven

Teacher: Let me put it to you differently. If I gave you 2 apples, and
another 2 apples and another 2, how many will you have?

Johnny: Six. 

Teacher: Good. Now if I gave you 2 cats, and another 2 cats and another 2,
how many will you have?

Johnny: Seven!!!

Very angry Teacher: Where do you get seven from?!?!?

Very angry Johnny: Because I  already have one at home!!!