Gestational Age based on Ultrasound or LMP?

Hi mga mommies and mommies to be. Ask ko lang po kung normal lang na may 1 week gap ang gestational age based on ultrasound and LMP? Mas mataas yung weeks ni baby based sa ultrasound vs sa LMP ko ng 1 week. LMP: 18 weeks 3 days Ultrasound: 19 weeks 4 days Thank you!