1 answer
The character limit is custom code in your org not including managed packages. The count may not match for several reasons including namespaces, installed packages, presence (or absence) of code classes, and the contents of the code classes.
As for code coverage, the 75% needed applies to unmanaged code only. You can use Developer Console or the AppExchange package Admin Test Runner (paid, but you can install it in your sandbox for free) to see the details of your test coverage.