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The pattern is having you increase 9 sts approximately evenly distributed across the row. Maintain the seed stitch at the side edges and in the center panels since that will continue for the rest of the blanket. Make sure the other increases will be part of the cable patterns on the next row. You won't maintain seed stitch there on the next row anyway.
On the increase row, make the increase but don't count it as a knit or purl. Work the stitch following the increase as you would normally do. If it's a knit, purl it, if it's a purl, knit it. Yes, that'll mean for example, a knit next to an increase knit but it won't be noticeable once the cable pattern starts.