Why is the scale for a Sphere Collider radius not matching that for Transform?

I am taking a look at my sphere collider for my enemy paddle in this 3D clone of Pong to see if my minimal speed limit in the X-axis of my ball is high enough so that it intersects the collider when moving towards the north wall, exits the collider right before it hits the north wall, and then afterwards, goes back to the collider.

The sphere collider I’m using is actually a trigger for the paddle to detect the ball, and in this case, to predict where the ball will be (in terms of Y) by this X position, which is where the paddle is. I’m going to use raycasting and simple scaling on the reflected vector (if it hits a wall) to predict where the ball will be within the opponent’s strike zone.

But there’s something peculiar on how the sphere collider radius is set up. My paddles are set 4 Unity units away from the origin, I have my sphere collider set with a radius of 17.5, where in the Scene View, the collider that goes beyond the player’s paddle is not passing through the far edge of the playing field, which is 10 Unity units long (my enemy paddle is sitting one Unity unit away from the edge of it.)

I don’t know what this is, but I feel like my sphere collider radius in values of Unity units is 8.75 and not 17.5 as I figured.

Wondering if this has to do with my scale for the paddle itself, as the sphere collider is the child of the paddle.

Use a mesh-collider instead.