Problem with my polaroid back?

I just recently acquired a polaroid back for my Contax 645. Today was the first time that I used it and had some confusing results. I loaded the film and first pulled out the black piece of paper. Then I pulled out the white tab with the number 1 on it. I shot the picture and then pulled out the print waited 90 sec and separated the print, and it was black. So I figured I had messed up some how. I repeated the steps and and took a photo of a different subject. However the next picture that came out was the first one I shot. Then the entire rest of the role was always one picture behind. Is it supposed to happen this way or not?
The print is also a square, and not the in the shape of a 645. I forgot to pull the white numbered tab out once and since it was one photo behind it double exposed it. That print came out crappy but it was no longer a square format but now a 645 format. I am confused and any help is much appreciated! Thanks in advance

Don't pull the numbered tab first. You have to take a picture THEN pull the white tab THEN the black tab that has the picture part.

Problem solved! Thanks