As written, the buttonholes are right beside each other. When wearing, one will be toward the inside of your legs and the other one will face outwards.
The left leg buttonhole round directions are - K1, BO next 3 sts (buttonhole placement), k1, p1 to end of round.
The right leg buttonhole round directions are - K1, p1 to last 4 sts, BO next 3 sts, p1.
When you knit in the round the beginning and end of the round are beside each other. As written they’re only 2 stitches apart, don’t end up equidistant from the centre of Chart A, plus the left leg buttonhole stitches are p1, k1, p1 and the right leg buttonhole stitches are k1, p1, k1.

Think of a clock, with 12 as the beginning of the round. So the left buttonhole sits between the 12 and the 1 and the right buttonhole sits between the 11 and 12!! Basically side by side.

Well, one rep of the pattern is only 3/4” long, not 1”, so it’s a good thing I have shorter legs! 12” with the cuff folded (14” total) should be long enough. That would be from just below my knee to my ankle.

After 10 reps of Chart A it’s 11-1/2” long. Now I’m going to switch to Cart B.

I needed to switch things up to get everything lined up, including Chat A, and working together much better than this.

All issues fixed.

The leggings weigh 103.5g.
Before blocking the leggings are 13-1/2” long. The 1 x 1 rib is 8” in circumference, Chart A is 7-1/2” in circumference, Chart B is 7” in circumference.
After blocking the leggings are 12-1/2” long x 8” in circumference on the top ribbing and the main pattern. The bottom ribbing is 7” in diameter.

Size medium (12-1/2” - 14-1/2”’), the smallest size, is too big so I’m going to use fingering weight yarn and see if I can get a gauge of 7 sts/“.

I’m going to need more than a 3 stitch buttonhole because of my smaller gauge. It’s not going to be anywhere near as stretchy as the ribbing over the amount of stitches I need, probably 7 stitches, so I’ll mark the stitch to sew the button on once I’m done.

My calf is 12-1/4” and my ankle is 7-1/4”. I might need to decrease before the ankle.

With 3.5mm needles I got a gauge of 24 sts/4” (6 sts/“). With 3mm needles I got a gauge of 25.5 sts/4” (6.375 sts/“). I got a gauge of 7 sts/“ with 2.5mm needles. Perfect!