When piece measures 181922 cm approx 455 cm remain insert 1 marker in each side so that there are 182023 sts both on top of foot and under foot

Can you repeat this sentence, but add in punctuation?
When piece measures 18-19-22 cm (approx. 4-5-5 cm remain), insert 1 marker in each side so that there are 18-20-23 sts both on top of foot and under foot.