Knitting charts and thumbs

Hello, What a wonderful site!!!
I’ve been knitting mittens for years on dpn. but the same pattern, I’ve adjusted it here and there and its been great…Then I decided I wanted to try something a little more difficult and purchased a book on Folk Mittens! I was so excited!!! until I realized all of the patterns are done in charts. (wow this is truly a challenge… I might have to knit a few more pair of mittens in my old pattern just to reassure myself I can make a mitten)
I understand starting the chart in the lower right hand corner and the symbols for the different stitches, but I don’t understand the vertical column in the chart to make the side seam gore, where it says to knit waste yarn in for these stitches for the placement of the thumb. (I’m use to doing a normal gore, increasing stitches after the cuff and then putting them on the stitch holder.) I’m having a hard time thinking apart from this way.
Any help in understanding the charting system would be greatly appreciated.

I can explain the thumb. You would knit X sts with the scrap yarn, put those back on the left needle and knit them again with the mitten yarn. Continue knitting the hand. When you’re ready to begin the thumb, take out the scrap yarn stitch by stitch as you place the sts on two of your dpns. There will be twice as many sts as you originally knit, an upper and lower set (or inner and outer). You will probably have to pick up an extra st or two in the gaps between the 2 sets; do it even if the pattern doesn’t mention it, you can dec them on the first round.

I saw an example of making the thumb hole by a woman knitting a piece of waste yarn on to the base stitches and then knitting over those loops on the round. When she was done with the hand she then removed the piece of waste yarn and just began to pick up and knit for the thumb stitches.

It was very much like a provisional cast on (if you want to think about it that way). However, she was not adding in any stitches to make the mitten “uniform” in stitches once removing the thumb stitches like you do when you leave them on a stitch holder. Which reminds me, I need to get one that is much small than the one I currently have.

I think I understand… and I’ll give it a try.
I’m wondering if I’m over thinking this… wouldn’t be the first time.
Thank you for your help.

Happens to me all the time. I am doing the other mitten with the waste yarn stitches in them and it makes starting the thumb soooooo much easier.