I am making a prayer shawl for a dear friend who is having a tough time right now. I do not understand your pattern. I believe there is something missing for the finished product.. It tells you to do row 1 and 2 until piece measure 36 inches on th diagonal side. You bind off loosely and block shawl. No where does it tell you to decrease so your shawl will look like a shawl. Hope I am making myself clear.
I found a post that may help you. By typing "prayer shawl" in the search box at top right page you will get to the page. Click on the 7th one down under chewchew dated Oct. 18, 2011. I don't know which shawl you are doing exactly because you didn't mention.
And all the women who were wise of heart spun with their hands, and they kept bringing as yarn the blue thread and the wool dyed reddish purple, the coccus scarlet material and the fine linen. Ex. 35:25