Ay, ganyan ang dating ng ultrasound reading nila! Yung 3 1/7 weeks ay ibig sabihin 3 weeks and 1 day ng pregnancy mo, so basically, your doctor is being super specific about kung gaano kalaki na ang gestational sac or embryo based sa ultrasound measurements, kaya nag-add sila ng extra days para accurate. Hindi ito malayo sa expected dates usually, pero best ask your OB kung bakit nila ina-adjust, kasi minsan may slight dating changes pa kung hindi accurate ang last period mo or if there's any concern they want to monitor.