Kim Hargreaves Fain. Armhole shaping.

Can someone explain…”co 3 sts at beg of next 2 rows…Dec 1 st at each end of 3rd and foll 4th row”.
I understand the first part. Now when it says Dec 1 sts at each end of 3rd foll 4th row. Do I count the 2 previous rows as row 1 and 2. So next row I would dec? or do I continue in pattern and dec on the next 3rd row and foll 4th?
I’m getting better at understanding British patterns but always overthink.
Help.

Welcome to the forum!
Cast off 3 sts at the beginning of rows 1 and 2. Then dec at each end of row 5 and row 9.

It’s a little open to interpretation but that seems to distribute the decreases best.

Thank you that’s what I thought.