Priority date..

[MiMi]

Hi,
My question is about priority dates. I am Canadian citizen and just became the spouse of a U.S Citizen, i read that in my case i am not supposed to have a priority date but i have one. They say they got my application I-130, I-485, etc.. on June 22th 2006 but i recently got my aos interview letter and on it i have a priority date which is june 16 2006 same as the received date. Why do i have that priority date? Can somebody help me to understand better all that please? Thank you!