Am 8weeks along went for a ultrasound today but they also did a transvaginal ultrasound.everything was normal ?

there was a yolk sac, fetal tube and fetus measured 12.3mm from crown to rump.they also did a transvaginal US because the couldnt see any cardiac activity and the results were same.the US said the fetus is 7weeks 4days though according to LMP im supposed to be 8weeks.am scheduled for another scan in a week.im devastated and worried