Why the priority date is empty/blank on I-797C Notice of Action

I am under I130 (F2B) category. I received my Notice of Action I-797C where received date is May 2007 and notice date is June 2007. But there is no priority date. Its is empty/ blank. I am confused. The notice mentions that USCIS received the fees $190 and I can check the processing time at www.uscis.gov . Why there is no priority date? Does this mean a lot delay? I am not staying in the USA.