Quick help w/ pattern please

I am making the 2 needle mittens from lion brand yarn website. This is my next instructions:
k12 (14, 17, 20) — 24 (28, 34, 40) sts. Cont in St st until piece measures approx 5 (6, 9, 10)” from beg.

So there are 17 stitches left on my needle because that is the size I am making. So I k17 like the instructions say, but what does the dash above mean?