They don't go by weight, they go by Height, and I was thinking the same thing

JCarlson's baby is such an adorable, teeny, tiny little baby!!! This chihuahua is 4inches tall which is smaller than the one currently in the Guinness Book of World Records...That's why if he's still the same height when he hits his 1st birthday next month, he will prob go into the book.
This was in the Orlando paper.