It's worded backwards, try this -
Inc 1 st at each end of the next row and every foll 8th row until there are 53 sts. You don't need to worry about the 'work into garter st' part, just inc at both ends of the row.
Then after you have 53 sts, just knit it without increases until it's 24cm from the cast on. Mark the sts at the ends of that row with another yarn, a safety pin, paper clip, and do another 8 rows and bind off.