Physics2D.OverlapBoxNonAlloc not return all overlapped collider

Hello, I have a problem with the method Physics2D.OverlapBoxNonAlloc.
Actually I used the command like this:
int num = Physics2D.OverlapBoxNonAlloc(Position, new Vector2(Width, Height), 0, collider2Ds);
where collider2Ds is an array previosly allocated.
In a overlap situazione like this, where box is egual to the position and dimension of box 2, the only collider returned in the previous array is the collider 2 and not also the collider 1.

Yes, I confirm that the array is big enough, because, in this case, I have only three colliders (the third is not showed in the image) and the array is allocated in order to receive three colliders.