Shaping sleeve

I have a question about my pattern.Where it says then ,bind off 2sts at each side until the piece measures 55cm, do I keep binding off 2sts each side or do I do it once? Here is my pattern

When sleeve measures 49-49-47-47-45 cm bind off for sleeve cap at each side every other row: 4 sts 1 time, 3 sts 1 time, 2 sts 3 times, 1 st 0-0-4-5-8 times,( then bind off 2 sts at each side until the piece measures 55-56-56-57-57 cm) and then bind off 3 sts 1 time. The piece measures approx. 56-57-57-58-58 cm, bind off the remaining sts.