This could be helpful.
https://www.janome.com/siteassets/bl...g-basics-5.pdf
I sew on Brother sewing machines. When I want to sew something other than 1/4" like 3/8", I use the general sewing foot and usually move the needle to the left until the edge of my sewing foot lines up on the edge of the fabric I am sewing and I get my full 3/8" that I need. Or you can use a seam guide like blue tape and just sew with the needle in the middle. Or on the feed dog plate, you will see measurements. These are small lines that have labels to tell you how big the seam will be if you run the fabric along the edge of the line and leave your needle in the center while sewing. (I get into trouble when I have to go around corners using this method.) If moving the needle, make sure you don't have a single hole plate on your machine. It's a great way to break a needle.
All this sounds confusing, but it really isn't that bad. Get a piece of practice material and figure out which method works the best for you. For me, it is moving the needle and being able to line my fabric on the edge of my presser foot. Otherwise, I can sew a very crooked line. "smile"