Help with EZ's Baby Surprise Jacket

Can someone please help me figure out the Baby Surprise Jacket? I have the instructions and the DVD and I totally understand the instructions. The part I don’t understand is how to figure out how to make a specific size. In Elizabeth’s pattern 6 sts/in makes a newborn size, so if I wanted to make a 3, 6, of 9 month size how many stitches/inch would I use?

I have tried searching the internet for a sizing chart, but no luck. Has anyone figured out some kind of chart to use for the different sizes?

Thanks for the help!!!

You basically change the needle size and yarn thickness to get different sizes. Here’s a wiki on the BSJ that shows what gauge makes which size -

Thanks for the help Sue!!!