Calculate apps via Ultrasound

#advicepls Hello po! Magtatanong lang po sana ako Imposible po ba na minsan mali po yung ultrasound duedate . ? Kasi po itong apps na to na dinownload ko cinalcute kopo yung last mens ko po . November 3 po kase last mens ko po . So calculate kopo sa apps nato lumabas po is August 10,2021 Pero Nun 3rd Ultrasound kopo is September 13,2021? Imposible po ba mas maaga manganak bago magseptember 13,2021 po??????? Sana po my makapansin po helpp po need ko po advice o sagot po.... Salamat po