Thanks for the advice, but I'm afraid I mis-typed something.
For Rounds 5 and 6, under the Bias Ribbing section, there should be a Kfb at the end of the rows.
So the Bias Ribbing section of the pattern is as follows;
Rounds 1-4: *K1, P1, repeat from * to last stitch
Round 5: K2tog, *K1, P1, repeat from * to last stitch, Kfb
Round 6: K2tog, *(P1, K1), repeat from * to last stitch, Kfb
The mittens are not decreasing each round, but I still can't figure out why it's going wrong. Round 5 always comes out fine, but when I start Round 6, the bias ribs are never lined up the way they should be....hence the confusion over how many stitches to shift and in which direction.
Any ideas ?