Gauge Question and changing yarns

I am making these leg warmers.

website is

bohoknits. blogspot .com and they are called “abyss legwarmers”

I am new and they wont let me post a link yet. Sorry

I have never made anything that required gauge and exact size before so I am confused.

I picked a worsted weight yarn so they would knit faster and be chunkier. She recommends in the comments to only cast on 64 stitches instead of 80 and use a size 6 instead of 2/3 needle size. So how do I make a gauge to check my size and adjust accordingly?

I knit a swatch and in 2 inches i got 10 stitches with a size 4 needle but do i still want the same gauge she says since I reduced the amount of stitches cast on???

Thanks

Here’s a link - http://bohoknits.blogspot.com/2010/12/abyss-legwarmers.html

Okay, it says the gauge on the larger needles and heavier yarn is [FONT=Arial,Helvetica,sans-serif] 22 sts = 4" on 4 mm [/FONT][FONT=Arial,Helvetica,sans-serif]So that would give you 5¼ sts per inch or 11½" around. If you have 5 sts per inch, 60 sts is almost 13" around. [/FONT][FONT=Arial,Helvetica,sans-serif]Your worsted yarn is thicker and that’s why you get a larger gauge even with the same needles.[/FONT][FONT=Arial,Helvetica,sans-serif] If that’s larger than you want, then cast on less sts in increments of 4, so you could use 56, 52, or 48. Also, it’s a good idea when knitting for the gauge to use more sts for more accuracy. But for smaller items like these, you could just cast on and knit 3" then measure to see what the gauge is and how large they’re coming out.
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It says that they are approximately 5 inches wide (lying flat), so you want to have enough stitches to measure 10 inches around. Sound right?

You said you got 5 stitches per inch, so you’d need 50 stitches around for a 10-inch circumference. If you want to adjust that measurement, just reduce or increase 5 stitches per inch.

You don’t have to worry about row gauge for these since they are knit to a specific length rather than calling for a particular number of rows.

But she has to reduce by 4s because it’s a k2 p2 rib.

I think I got it figured out with all your help. I was so focused on the gauge swatch directions I didn’t look at the finished size and just figure it from that. Thanks so much. I am pretty new at knitting and loving it.