How to find the percentage value from A to B when I know the X value in between these two points?

I created this picture to kind of illustrate what I mean better.

[![enter image description here][1]][1]

I wrote this function which gets the percentage, but how do I also include the center offset?

    private float GetPercentage(Vector2 point, float radiusOffset, float centerOffset)
    {
        float radius = Math.Min(circle.rect.width / 2f, circle.rect.height / 2f);

        radius *= radiusOffset;

        return 1f - (Math.Max(Math.Abs(point.x), Math.Abs(point.y)) / radius);
    }

The radius offset is from 0-1, 0 being the 0,0 position and 1 full radius. The center offset is from 1-0, 1 being the 0,0 position and 0 being the radius border.

  [1]: https://i.sstatic.net/veLXK.png