Help with this mitten pattern!

Hi, I am working on this mitten pattern , but I am stock in the part where I have to knit the thumb. This is what do not make sense to me:

Shape thumb gusset: (…)
11th row: K5. P2. K2. C4F. P2. K13. Inc1 in next st. K10. Inc1 in next st. Knit to end of row. 60 sts.
13th row: K5. P2. C4B. K2. P2. K27. turn. Slip rem sts onto st holder.

***thumb: next row: P16. turn.
Work across these 16 sts in stocking st until Thumb measures 21⁄4" [5.5 cm], ending with a purl row.

After row 13th, I end up with 18 sts in my needle, but to make the thumb I purl 16 sts.

Please I need your help interpreting this pattern!!


Here is the pattern link

Before the turn in row 13 you should have 18sts on the left needle and 42sts on the right needle. Turn and place those 18sts on a holder. You should now purl 16sts out of the 42sts and again turn. For the thumb, you work back and forth on these 16sts in stockenette stitch.