Casi, you can just use the size that is on the pattern for the pocket size.
I have made a few of these and you can alter all the sizes. I ended up getting rid of my bowtuck patterns because I don't even use them anymore(so I can't help you with original sizes). That's what I do for the bags I make now. I kept altering the pattern and came up with one of my own. I've also made mine without the pocket in the front, but I quilt all my fabric before hand on the longarm for more decoration.

Okay, now what about the line for the pocket to go onto the lining? Does that need to change?