Sleeve shaping question

My patternsays:
When the sleeve measures 50-49-48-47-44 cm bind off 3 sts each side of marker. Then bind off for sleeve cap at each side every other row: 3 sts 1 time, 2 sts 3-3-3-3-2 times, 1 st 1-4-4-5-12 times, then bind off 2 sts at each side until the piece measures 57 cm, then bind off 3 sts at each side 1 time. The piece measures approx. 58 cm, bind off.

I did this and it turned into a much too shallow sleeve-cap. Am I mis-reading this? When it says “Then bind off for sleeve cap at each side every other row: 3 sts 1 time, 2 sts 3-3-3-3-2 times, 1 st 1-4-4-5-12 times” I decreased on the purl row on one row and on the knit row on the next. Was that wrong? Was i supposed to just do the decreases on the purl rows? I’m confused b/c later it says to BO 3 sts at EACH side 1 time. I think that’s what I’ve been doing.

Read literally, the translation would have you BO on both ends of the row, but you can’t so you do it over 2 rows. These translated patterns are tricky, you have to first BO 3 sts on the next 2 rows, then 2 sts over the next 6 rows, and then you can just dec 1 st instead of BO, at both ends of the row, for however many rows.