When I'm Looking in a Mirror – am I Looking at Glass or at the Reflected Image?

Let’s say I want to look at something that’s 20 feet or more away. I lamp is 20 feet away. A mirror is 3 feet away, but it reflects the mirror on the other side of the room. When I look at the lamp reflected in the mirror, am I looking at the glass that’s 3 feet away from me, or are my eyes physically perceiving something that’s 20 feet away? Would eyes use the same mechanism to see a distant reflected image as they use to see an object of actual distance?