I've created a custom package that includes a theme some custom blocks. This was done more or less through following the 'Building a Concrete5 Site' guide in the docs.

From the very beginning the package appears in both 'Currently Installed' and the 'Awaiting Installation' sections of the Add Functionality page. Both show the same version number.

Why would this happen, and what have I missed from my code that may cause this to occur?