The game manual says that the level 1 habitat platform is 36 inches long, including the length of the inner rectangle as well as the small ramp at the end leading down. However, the field drawings say that the length of the rectangle alone is 36 inches, with the ramp leading down adding another few inches.
I would ask on the official FRC Q & A, but it’s not open until January 9th. How can we clarify this?
While I am not the Q&A System, if you check the CAD models for the field, it shows the depth of the platform as 36" prior to the lip down and 48" after the lip down. I suspect the game manual diagram was simply mislabeled. They’ll also be releasing a new version of the manual on Tuesday so as long as the pattern hasn’t changed, and I suspect it’ll be corrected then, so check back on Tuesday 
Adding on to this, the description of the manual on page 23 states that the deck itself is 3 feet deep.
The lowest deck and the ramp form Level 1. The Level 1 deck is 3 in. (~8 cm) high by 10 ft. 8 in.
(~325 cm) long by 3 ft. (~91 cm) deep.
So it seems as if the diagram has a minor error there.