Pattern Help

Trying to make a girls shrug. I’m having trouble understanding the front part with shaping the armhole. Any help is appreciated. I’m starting with 26 stitches

Shape armhole
Cast off 2 sts at beg and inc 1 st at end of next
row. 25(27:29:31) sts. Work 1 row. Inc 1 st at
front opening edge of 3rd and 2 foll 6th rows
and at same time, dec 1 st at armhole edge of
next and foll 2(1:1:0) alt rows. 25(28:30:33) sts.
Cont straight until 13(13:13:15) rows less have
been worked than on Back to beg of shoulder
shaping, ending with WS facing for next row.

When you come upon directions like this, it’s easiest to write them out row by row. Call the next row, row 1:
Row 1 cast off 2 sts, work to last st, increase 1 st
Row 2 work across the row in whatever pattern you have been doing
Row 3 inc 1 st at the front opening edge
Row 4 dec 1 st at armhole edge and at the armhole edge of the foll 2(1:1:0) alt rows (depending on the size you’re making)
Row 9 inc 1 st at the front opening edge
Row 15 inc 1 st at the front opening edge
Work all other rows in pattern
Cont straight until 13(13:13:15) rows less have
been worked than on Back to beg of shoulder
shaping, ending with WS facing for next row

Thank you for your help. I have a question on the following part below for the sleeves. What does foll-(18th;20th;-) row mean? I know foll means following but the hyphen doesn’t make sense to me.

SLEEVES
With 4.50mm needles, cast on 36(38:40:42)
sts. Beg with a k row, work in st-st,
shaping sides by inc 1 st at each end
of 11th(15th:17th:19th) and every foll
14th(16th:18th:22nd) row to 44(44:44:50) sts,
then on every foll –(18th:20th:–) row until there
are –(46:48:–) sts. Cont straight until sleeve
measures 25(29:33:37) cm, ending with RS
facing for next row.

The hyphen would indicate you skip this instruction if making the smallest and largest sizes. So after you have 44 or 50 sts, just keep knitting until it’s the right length. It’s like putting in 0 for the size.