First ultrasound

So, today i had my first ultrasound. Based on my lmp i thought i was 7w+6d, but when the dr measured the fetal pole, it showed to be about 6w+2d. I was a bit sad/disappointed, but the dr said everything looked fine and normal, the pregnancy is just earlier than we thought. The machine detected a 121 bmp heartbeat. She said to come in again next friday to make sure its growing at the appropriate pace and to measure it again to assign my due date more accurately. I'm a bit, i dont know, confused, but i guess i'll just have to relax and wait patiently for my little bean to grow ?