Neuchal Translucency Ultrascan

Had my 12 week scan today. Was so anxious but thankfully the neck fluid measured 1.5. Now just to wait 5 days for the blood work. I was told by a friend as long as the neck measures well the blood work should come back fine. Anyone have any thoughts on that? Also my baby is measuring 13w6d but according to this app I'm 12w4d and according to Ovia I am 13w. So strange. Each has the same date of the start of my last period. Or does it just mean I'm having a huge baby? 😂