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After the directions to bind off 2sts at the beginning of the next two rows, you're going to start the raglan armhole decreases. The row directions are telling you first how often to decrease and then, how to do the decreases. There's a mistake in the order of the sentences for the "how to" rows so no wonder you were confused.
How often to decrease
: dec 1 st at each edge every other row 9 (10, 11, 12) times.
How to decrease
Row 1: K1, sl1, k1, psso, k to last 3 sts, k2tog, k1.
Put remaining 18 (20, 22, 22) sts on a holder.