Item #'s - Missing the 4 but got a 7 as compensation =D

On the in-game HUD, our items are listed as 1-2-3 (top), 5-6-7 (bot).....

In key bindings it lists item's # 1-6 and nothing is changed in regards to how they are bound. Just 5 is 4, 6 is 5, and 7 is 6.