First ultrasound on 6 weeks 2 days

Pari

Hello friends, according to app I am 6 weeks 2 days and according to ultrasound I am 6 weeks 1 day. Also I see the hearbeat but not hear it. Is it normal that not hear the hearbeat on this stage. Is anyone is on the same boat. I saw many says that they hear the heartbeat on 6 weeks. But I could only see that.