help guys please

dayner 1.3.08 👩‍👦nov 6 2018👶🌈

just been for my second scan which I should be 7week and 2days .. but am measuring at 6week and 3days.. they saw a flicker of heart beat and everything looks fine ☺️ but I no my excat dates and should be 7week is this normal to be few days out ??