The Xbox One contains a 500gb hard drive, but of course that doesn’t mean you have full run of the entire capacity. Though the console doesn’t tell you how much space you’re using at any given time or what its limit is, IGN has done the math and concluded that you have access to 362-365 gb of space.
That would make for a significant cutoff — A Windows 7 PC with a 1tb HDD, for example, will let you use 931gb of its capacity, but the Xbox One interface and native apps apparently use much more than that. The reason for the range of sizes above, by the way, is the aforementioned lack of data management tools on Xbox One combined with how the thing they attempted to install that trigger the “you’re out of space” message was the 3gb Zoo Tycoon, and they didn’t have anything smaller left to try to install. Which means the true limit could be anywhere in there. And, yes, these are estimates based on listed file sizes, but it’s likely pretty close.