How many pounds should the baby weigh ?

I went to the doctors for ultrasound. I was 29 Weeks and 6 Days. This app we are on says she should weigh 2.5 pounds. They said she weighs 3 pounds. The doctor told me that’s normal but a little on the smaller side.

Then yesterday I go to the doctors again for an ultrasound and I was 33 Weeks and 6 Days. This app says the baby should weigh 4.2 pounds. The doctor tells me she now weighs 5 pounds and says the same thing. “That’s normal but a little on the smaller side”

So I googled and the numbers matches up with this app but the doctors are telling me something different 🤷🏻‍♀️