how do you change baby's weight on here?

Lizzy • I'm a first time mom to my handsome little boy who was born 8.26.17💙 he makes me incredibly happy. follow our journey and I'll follow yours!😘🙂
The weight is has for my baby is way off. And I'm not sure how to change it? Can you? 
Also I found out today my baby is a boy💙😍 he weighs 12 oz at 19+5days. What did your baby weigh at the time? :)