Help with anemoi mitten chart!

If anyone has made this mitten…the chart calls for putting the thumb sts on waste yarn, and then in the next row, CO1 st over those sts. I did that. Then on the following round, there is that extra cast on stitch that is not on the chart! What do I do with it? The chart doesn’t come out right because of it. Help! Sjr

Don’t cast it on. If you already have, you can knit it together with one of the other stitches, and later, when you do the thumb, pick up an extra stitch where the cast-on stitch would have been.

No it all works out - from memory, the thumb initially grew out of a single CC stitch, when you put the thumb stitches aside, that stitch is lost. So you cast on a new CC stitch. See that red box around the thumb stitches? On top of that vertical line of CC stitches in the red box, the line continues (so only the few lower stitches in that line are in the box). Your new cast-on stitch replaces the one lost, and it is the CC stitch. It’s the CC colour that makes a CC box around the whole palm pattern.
Does that make sense?

Yes, that does make sense. Before reading your post, I ripped out the row that comes after putting the thumb stitches on waste yarn a bunch of times until I finally got the right number of sts. How? I have no idea! Magic! (Or some horrible mistake). At least when I do this again for the next mitten, I will have some clue! Looking at the chart, there is the vertical red box around the thumb sts part within the main chart, then after the waste yarn row, there is a horizontal red box in the thumb chart itself that lasts for two rows. What does this mean? Thanks for your help. I am also going to have a big hole where the thumb joins the rest of the mitten for sure! sjr

You need to read the pattern notes - Eunny has made sure to explain the pattern and how to use the charts quite thoroughly: I love her knitting but her patterns are also well written and don’t expect people will know everything already! The red boxes are for adjusting the length of the thumb (like the horizontal red box on the hand part also). Let’s say you had very long fingers and thumbs, you would repeat those parts in the box a few times extra, as written it is for a smallish hand I think, so when you get to those parts try on the mitten and decide how long you need it to be, and those few rows are repeated as many times as you think necessary.
The extra thumb rows are done after the thumb is separated from the hand. When you have finished the hand and come back to do the last part of the thumb, you join into a round, and you knit those two rows in the box.
The next rounds are decrease rounds, but if your thumb is not short enough for that and you want to make it longer, you don’t have to start decreasing yet: do those lines in the red box as many times as necessary.
Do persevere - the mittens come out really stunning. I love Eunny!