Help on shaping armholes

I don’t understand what I am supposed to knit on the following pattern for shaping armholes:

Cast off 2 sts at beg of next 2 rows. 73 sts (ok here)
Next row (rs): k2, k2tog, k to last 4 sts, sl 1, k1, psso, k2. 71 sts. (Ok here)
Last row sets the decrease.
Working decreases as set, dec 1 st at each end of 2nd and foll 3 alt rows. 63 sts ( I am lost here) Cont straight until armhole meas 22 cm, ending with RS facing for next row. ( ok here)

I am lost on the working of decreases, can someone tell me how to knit this part of my pattern. Thank you!

Hi, Following on from the RS decrease row, work the next WS row (row 1), decrease as you did before on the following RS row(row 2 or 2nd) work the next WS row(row3), decrease on the following RS row (row 4 or 1st alternate) and continue doing this another 2 times.
Hope this helps and good luck with your project :grinning:

Thank you!!!