I think that this picture helps us visualize what is actually happening in screen space when we are doing texture mapping. The really small square is giving us a lot of detail and color of what is actually projected from texture space. On the other hand, through Minification, we see that more pixels from the texture space play a role in the resulting image in the screen space. Thus, I think through minification we get a more blurry result and magnification provides us a more clearer representation of the texture space point that is being mapped.