How do I open the safe?

Hint 1 of 6:

There are two safes in the room I am referring two.

Hint 2 of 6:

I am talking about the ones that DOESN'T require the red card.

Hint 3 of 6:

Go look at the desk.

Hint 4 of 6:

Hit the middle button.

Hint 5 of 6:

Now, look at the combination behind you.