Welcome!
You’ve presumably worked some number of rows before you came to this instruction. The “next row” is the one you are about to knit or purl. If you call that row, row 1 then you would inc at each end of rows 5,9,13,17,21,25,29 etc until your reach 109sts.
Remember too that you’re increasing 2 sts per increase row, one at the beginning and one at the end of the row.