I pulled an FDE Type 1 RMR 06 (3.25 MOA) out of my safe that's been there a couple years and mounted it on a new pistol.  After messing around with it a bit I thought the dot appeared large.  I pulled out my mounted Type 2 RMR 07 (6.5 MOA) and confirmed what I thought.  On the same brightness setting the smaller dot actually appears twice as large.

What would cause this?  I don't have any eye issues like an astigmatism or anything.  Does it need sent in?