Fetching thumbs

I am making Fetching
and have a question. I noticed that some people have changed the thumb to one that has a gusset. What is the benefit of each type of thumb and if I wanted to use a gusset how would I modify the pattern. By the way this is my first pair of mitts. I don’t know why but this is way scarier than socks.:aww:

I did some digging on Ravelry and found the following, but I need a little help with it please.


Masterstroke’s modification are as follows:

I do have a better plan for the thumb gusset, which I stole from another pattern. Starting at the 5th row after the last wrist cable row:
Row 5: k2, m1, k2, p1, continue in 4x1 ribbing.
[COLOR=“RoyalBlue”]next row and all alternate rows, knit 4x1 ribbing and k new stitches picked up for gusset.[/COLOR]
Row 7: k2, m1, k1, m1, k2, p1 continue in 4x1 ribbing
Row 9: k2, m1, K3, m1, k2, p1 continue in 4x1 ribbing
Repeat the increase rows alternated with regular rows until you have added 15 new stitches.
Then: k2, put 15 new stitches onto waste yarn, k2, p1, continue in 4x1 ribbing and follow pattern through picot bind off.
To Make thumb: pick up 15 live stitches off waste yarn, pick up 2 stitches and finish thumb as directed. This makes a nice comfortable thumb gusset. The gusset adds some width, so for those with smaller hands, you may want to consider starting the pattern with 40 stitches instead of 45. I started with 45 stitches and my pair is a little loose, but they don’t fall off.

The part I am not sure I understand is in blue, where do I increase and do I do it the same for both mitts? Any help would be great.