I think I've got it. She's having you make the back neck of the sweater deeper than the front. So you'll work across the 40 stitches (or whatever stitches you have for your sweater--half the total around). Then you turn the work and rib back, but when you get to the end of the original 40 you take on another stitch, slipping it, from the stitches on the needle. Rib back and do this again, slipping on stitch on the end from the stitches on the needles that haven't been worked in ribbing yet. When you get to 52, I think it was, you then rib all around the neck for an inch.
"Trust the pattern!"
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IngridKH on Ravelry