Gestational age confusion

Hi ladies I know I'm not alone in this confusion. Okay so when I was 4weeks I also got this round empty sac which is normal and then next ultrasound it says 6weeks or 7days with fetal pole seen and after 2 weeks means I'm already 9weeks right? But I'm shocked cos the doc said its 7weeks so it made me asked her why its just 7weeks? She explained that they always read its minus 2weeks and its how they calculate the exact fetal age and gestation age is also different cos it the calender from the day of conception so this explained why I thought from the start (first ultrasound) I was already 7weeks but was told only 4weeks there but didn't knew she meant gestational age not fetal age

. I hope you understood what I wrote here so that you ladies with the same situation could relate and to worry less.

My present ultrasound (7weeks fetal age) no heart beat scanned yet the obgyn advised me to come back after a week to hopefully hear it.

This was my previous ultrasound

4weeks gestational age

And 7weeks gestational age

And 9weeks gestational age