Just got a rat terrier and am surprised she is so small.  Her mom was 18 lbs and dad was around 20 lbs.  She was 4.25 lbs at 8 weeks.  Is this really small or is she going to get a whole lot bigger? 

I'm hoping that she'll end up around mom's size due to owls and hawks in the area and am getting a little concerned she's not going to get much bigger than 10 lbs but have no idea how these little ones grow.  I know our big dog was about 17 lbs when we got him around 8 weeks and is now a swelte 85 lbs! 

Any info would be great!