You BO stitches, then in the first cable, dec 1 stitch, 4 times meaning over 4 RS row; there's not 3 decreased sts in each row, just 1 dec and the bound off sts.
At that point you don't need to do the cross stitches, so just knit them. If there's still 8 sts in the cable area, just k3, k2tog (or ssk) k3. The next RS row, k2, dec, k2, and so on.
sue- knitting heretic