Having a a problem with the license!

Now i was reading the agreement now carefully untill i encountered this it kinda confuses me, well actually it does confuse me!here it is the extract of the agreement"(b) Once a Game is delivered to Licensor hereunder, Licensor shall have unrestricted rights to use, modify, edit, license and sell the Games through any and all electronic media now known or hereinafter developed, throughout the world, including without limitation through the Website, through electronic delivery mechanisms, and in "hard" or "box" media formats for a period of five years from the first commercial release of the Game. Licensee maintains sequel rights to the Games, where sequel is defined as changing more than 50% of the content of the original Game. "it says that you have unrestricted rights to modify edit, what does it mean , does this mean if i make the game you can change it the way you want it, also how we have to change 50% content of ours sequels to our own games, you mean game content or engine content!
An example let say i created a game. a racing game, my sequel would be another racing game with more cars and new tracks, how do you measure that 50%

This may have been asked before, i search not found any on this but anyways can someone help me clarify this part of the agreement.
thanks