It normally means to stay in the stitch pattern for those rows, without any increases or decreases, in this case, to just knit the knit rows and purl the purl rows, without doing anything else. But there's something wrong with the pattern:
(I'm going to use the smallest number for an example)
Transfer 20 (22, 24, 26, 28) held sts of one sleeve to needle. Do not join.
You start with 20 sts
Row 1 (RS): K10 (11, 12, 13, 14), place marker, k to end.
Row 2 and all even rows: P.
Row 3: K to 2 sts before marker, ssk, sl marker, k2tog, k to end.
This decreases by 2 sts. Now you have 18 sts.
Row 5: Kfb, k to last st, kfb.
This increases by 2 sts. Now you have 20 sts.
Row 7: As row 3 (18 [20, 22, 24, 26] sts).
This will descrease by 2 sts. Now you have 18 sts.
Work 21 rows even.
Here is where you just knit the knit rows and purl the purl rows without doing anything else.
Row 29: K to 1 st before marker, yo, k2, yo, k to end.
This will add 1 st, decrease 1 sts, then add 1 sts, giving you 1 more st in all, therefore ending up with 19 sts.
Row 30: P.
Row 31: K.
Row 32: P.
Rep rows 29-32 twice more (24 [26, 28, 30, 32] sts).
If you only increase 1 st in each of these 4 rows and you do it 3 times all together, you would only increase by 3 sts total, but they want you to have increased by 6 sts. Also, row 29 is odd in that you are doing this yo k2 yo around the marker. . .