maltese standard for full grown dogs is 6-8lbs or something. in the dogster website...people are putting 1-10lbs. because their dogs fall in that weight class. when sprite and ellie were 8 months old...they were around 3-4 lbs. i think. full grown they're 5.6 lbs and 7.8 lbs.
As I said Pixie is 8 months old and I weighed her on the bathroom scales the other day and she came in at just over 6lbs. I must buy a digital scales because the standard one might not be that accurate. A small bit concerned about her weight she may be a small bit over weight.
The only thing to worry about would be if they are a healthy weight. You want them to be not fat, or too thin. The size they grow to be in height will determine that. Of course if you are showing there is a limit.
Frosty varies between 10-11 lbs. and not an oz. of fat on him. He's just a big boy.