Understanding a pattern

I am learning to knit my first sweater, as everyone and their uncle has my hot pads. LOL. Anyway… The pattern is for a very simple baby sweater by Sirdar 1752. It is the back of the sweater and the first row after I finished the bottom ribbing.

6th row: P7 [4:6:9:4:6], p2tog, (p6 [8:8:6:8:8], p2tog) 7 [7:7:9:9:9] times, p6 [3:5:8:3:5].
63 [71:75:81:89:93] sts.

I understand that the different numbers in the brackets are for the different sizes, but why would it start with purling 7 stitches for the smallest size, yet only 4 stitches for the next size up, etc. I am so lost and I only get more confused as I go on in the row. Please help interpret what this row means…… thanks to anyone that will take the time.

The numbers in the last set of brackets is the stitch count. This is the total number of stitches you should have on your needle after you’ve finished the row. This is a check for you to make sure you’ve done it right.

The directions are going to be different for each size. For one thing, the sweater is going to be longer lengthwise and wider then the smaller sizes. The armhole shaping is going to be different, too. You will have a longer and larger armhole opening for the larger sizes then the smaller. Makes sense. So the shaping for this would be different on each size.

The initial p7 in the smallest size partially compensates for the reduced number of pattern repeats later in the row. In the end, the total number of sts will be graduated by size.

Of course!!! I was stuck on the very first purl and if I had just looked at the row in its entirety, I would have seen that the total number of stitches actually do increase for each size by the end of the row. Lesson to learn…with the help of the generous bloggers on this site. I think I’m going to be spending a lot of time on this site…

Thanks again for the help.