First time knitting a sleeve, help with pattern please

Can someone please explain this pattern to me? Thank-you
Work in 13 rows rib (I understand this but not the below)
Rib 4, incl in next st * rib 3, incl in next st, rep from * to last 6 sts, rib to end 47 sts.

Work 4 rib stitches, do an increase stitch.
Now repeat 3 rib sts and increase in next sts. until 6 stitches remain on needle.
Rib the last 6 stitches.

Thank you, I understand now.