The numbers in the brackets are for the different sizes. So, it depends on what size you're making for what number to use. For this example I'll use the middle one.
You will start this row with Purl 4, then purl 2 together,
Next Purl 6, and purl 2 together. Do the Purl 6/purl 2 together 7 times across the row and end with purl 4.
Your numbers will probably be different than mine, depending on what size you're making.