Hitchhiker, I have a 64 bit OS.
The 64-bit is the default download so just click the blue button.
As regards 3.0.12 and 3.0.13 a mistake was made in the coding whereby the automatic update failed. Users were advised to download 3.0.13 manually. However, another problem appeared whereby 3.0.13 wouldn't run properly on Windows 8.1. That was later fixed in version 3.0.14. Some other minor problems erupted later and most were addressed with the release of 3.0.16.