Hi
I have been doing some searches on the internet for the creative grid rulers and realized where your original question might have come from. If I am being overly simplistic here, I apologize; I just don’t know what your skill level is.
First, before any batting or backing is added to your pieced quilt top you will square your pieced quilt top. Here is the advantage of making sure each block you make is square. If you have sewn accurate 1/4 seams, each block should be pretty square and if it’s not, it gives you a chance to correct the problem before you get too wonky of a quilt top.
Once your quilt top is square, you measure your backing and batting to be at least 3 inches wider on all sides of your quilt top. Example: If your quilt top is 84 x 90 inches, you would cut your batting and backing at 90 x 96 inches. Center your quilt top leaving a 3 inch margin around your quilt top. After you have centered and basted you layers together your quilting takes place. Having that extra margin around the quilt top allows for any minor movement or possible stretching that might occur during quilting. If you are making small quilts you can reduce the width of the margin around the quilt top proportioned to the size of the quilt.
Here where I think you might have gotten confused. Once all the quilting is done, you can measure 1/4 of an inch away from the edge of your quilt top onto the batting and backing and trim the rest of it away. However, if you are going to do this, you need to do the trimming before you sew on your binding so don’t accidently cut you binding. Once trimmed, you will line up the raw edge of your binding with the raw edge of your quilt top and sew a 1/4 inch seam allowance.
Not everyone does it this way. This way is suggest so the binding is filled out and supposedly wears better over the life of the quilt. Most people just trim the batting and backing off right next to the edge of the quilt top, then bind.
Here are the links to a couple of video which I think will help you make sense of what I just wrote.
https://www.youtube.com/watch?v=dnARfOO5otE
https://www.youtube.com/watch?v=VgaXP6kd8bc