Gathered Pullover

I have a questions on the shaping of armhole and neck.
Shape armhole and neck:
Next row: (RS) Knit to last 4 sts, ssk, k2-1 st dec’d. Rep last row every other row 10 mores times, then every 4th row 3 times.
The first section I decreased every knit row for 11 times and ended up with 15 sts. The second part is what stumps me. If I decrease every 4th row, I would decrease on a purl side. Is this correct? If I decrease on every knit row I think the armholes would be to big.
Thanks in advance for you help.

Let’s say for an example that your final decrease was on row 11–an odd/knit row. Every 4th row after that would be row 15, 19, 23, 27–still a knit row.

Thanks for the quick reply Ingrid. I get it now.