working in st-st: stockinette stitch, meaning knit a row, turn, purl back, turn, etc

When you get to the 5th row, which will be a knit row, increase one stitch at the beginning of the row - knit 1, increase, then knit across to the 2nd to last stitch, increase, knit the last

Keep going now purl row, knit row, purl row, knit row, purl row, then do the increases in the next knit row

Keep going until you have have done that 23 times

Then only do the increases every eighth row. Do the eight row set twice, for a total of 25 sets of increases

I concur.

Unless you are knitting the second largest or largest size (the pattern is clearly for four sizes), in which case you would do your first increase row then do your increases on a knit row with seven rows of purl and knit in between.

I agree with colleen...you don't; increase on row 5, and row 6 and row 7....you increase on row5, then knit 6 rows and increase....etc.

Nobody suggested increasing every row, not that it matters since the OP appears to have been a flyby.