Unlike the one-pager, which should be kept to one page, the ten-pager is more a set of guidelines than a strict policy. It's more of a "ten-pointer" than a ten-pager, but feel free to dedicate a page to a topic.
What's important is that all the broad strokes of information are included and the document is accessible and exciting to read. The foundation of this document will turn into your pitch and GDD.
Include a graphic if possible, a title (preferably a logo) and your contact information, target platform, target audience, target rating, and expected shipping date.
Page 2 should include a few short paragraphs about the story (beginning, middle, and ending ... or at least a cliffhanger) mentioning the setting, the characters, and the conflict. Gameplay description should give a brief idea of the flow of the game—break it into stages or bullet points if its easier to convey info that way.
How does the player grow as the challenges increase? How does this tie into the story? Briefly describe how these systems will work (experience points, money, score, collectibles) and what the player gains as they grow (new abilities, weapons, additional moves, unlockables).
Who does the player control? What is his/her/its story? What can they do that is unique/special to this game? Can the player do several types of activities? (Driving, shooting, and so on.) ...