Modifications:

I worked 1 x 1 ribbing at the wrist for 20 rounds instead of 16

I made the reverse stockinette section 9 stitches on each side of the thumb gusset instead of 11

I did the thumb gusset increases every 4th round instead of EOR and increased to 15 gusset stitches instead of 13

I worked 10 rounds of 1 x 1 ribbing before binding off

For the thumb, I worked 5 rounds plain after picking up 3 stitches, then worked 4 rounds of 1 x 1 ribbing

I turned the mitts inside out so that the stst side is the public side with the thumb gusset in reverse stst