iPhone 5s Compass and Level Readings are Incorrect
According to tests done on the iPhone 5s using the compass and leveler, it is incorrect. The compass is off by about 8-10 degrees and the leveler is consistently off by 2 degrees every time. It is unclear why the app is doing this. Most likely, this could be fixed with a software update. Apple has not commented yet on this problem.
Source: Cult of Mac