Source, One-to-one, One-to-one (keep incorrect)

I can't notice any differences between these. How are they different?

Dotted Small, Dotted Big

These seem similar, but I'm still not entirely sure how to use them.

They seem to overlay the intended pixel colour in the center, and display the current colour of the pixel a couple shades lighter. Is this correct?

What advantage is conferred by altering the current colour of the pixel?

Possible bug: If the intended pixel colour is white, but the current pixel colour is grey, this is lightened to white when the template is applied. There is no way to tell that the pixel is the wrong colour while the template is on.

Is this a bug, or am I not using them correctly?

Thanks!

Edit: After the server maintenance on July 13th, it seems the bug has been fixed.