I do not measure the very edge of a quiilt - especially if it is made up of many pieces - because sometimes it gets distorted a bit with a lot of handling. Because at times I am a member of the OCD group, I do take three measurements and average them. One in the center, one a foot or so from the left edge, and another measurement a foot or so from the right edge.
I like the turquoise color you have chosen for the inner border. It enhances the brightness and cheeriness of the center.