Knitting pretty book by Kris Percival

on page .63 directions for slippers.
To start with I may of made a mistake by using size 10 mm needles Canadian. Then I realized this is an American book. There was no guide for this that I could find.

I don’t know whether anyone out there has ever used this pattern but I thought it would be a good starter for a beginner knitter.

To be honest I don’t know where I went wrong but I have ended up with one side at the back near the heal longer.

Toe came together OK and I could sew up the heel area but I would have a flap on one side.

What did I do wrong?? GRRRR

Can you take out the side that came out longer?