Understanding Ultrasound Dating & Estimated Due Date (EDD)

Question
So why when i count back the weeks on my ultrasound it puts  me around my lmp? so does that mean my lmp was implantation bleeding since you says you dont subtract two weeks from ultrasound? i didnt miss my period til november so im confused on what info the ultrasound gave me.

Answer
If your USG says that your baby is 12 weeks old as on today, i.e 19 mar. Then you subtract 12 weeks from today to get an approx of implantation. From that day, subtract 2 more weeks to get your LMP. So in our example, the implantation would be around 19 Dec and the LMP would have been around 4-5 pf December. I hope  things are clear now.