What's the Deal with Fuses 53 & 54?

On a 2004 E320, there is a Fuse box under the hood on the driver's side.

Fuses 53 & 54 have three slots so the fuse can be on the left two slots (A) or on the right two slots (B). All the slots on my car have connectors to connect to the fuses.

What's the deal with that, and what are the differing slots for?

As you may know, I am having problems with our Local Emissions testers computer talking to the Car's computer.

My fuse 53 is in slot B instead of being inline with the rest of the fuses. I am wondering if that puts it into some kind of test or protected mode.

I am including a link to a picture of the fuse box so you can get a better idea of what I am talking about.