anyone know why or how

Dev 🍃 • Momma to a beautiful toddler, expecting a little handsome little boy in December 💙👶🏼 | taken 💞💞
The app says I am 24 weeks and 4 days but today they told me I am 25 weeks because of my measurements and my ultrasound. so which is it? & how do I change it to match the doctors because that's kinda confusing even though it's still the same due date?