While @mr-flibble is correct that this might be a browser caching issue, it sounds like in your case it’s more likely related to how Duplicati handles GUI based updates. Check out the “How Duplicati installs/updates work” block of the first post here for more details, but I’ve also included a summary below for your particular case.
Why a re-install still shows previous updates
On Windows an INSTALL (like from a .exe or .msi file) goes into your C:\Program Files\Duplicati folder as your “base version” and is what “Windows Apps & Features” will report as your app version. When the “base version” is run, it first checks an updates folder to see if there are any newer versions in there and, if so, passes control off to the newer version.
New versions get into the updates folder when they are installed via the Duplicati GUI. Since they weren’t actually “installed” (in the Windows sense) and aren’t in the C:\Program Files\Duplicati folder Windows doesn’t know that they’re there so just reports the “base version” number.
This also means that when you uninstall Duplicati what you’re really doing is removing the “base version”, but if you don’t remove the newer versions from the updates folder, then when the freshly installed “base version” (in your case 2.0.2.18) is run it detects the 2.0.3.6 update left over from the previous install and passes control to it. Basically, the uninstall process isn’t clearing EVERYTHING from the system.
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What’s up with Windows reporting v2.0.0.7?
With all that being said, I don’t know why your Windows Apps & Features is showing 2.0.0.7 but if it makes you feel any better, so is mine. 
I suspect there is a bit of a version reporting problem associated with Windows Apps & Features but a sample size of 2 is a bit small for declaring it a bug. If we can get some testing / confirmation from some other Windows users about what version shows in their Applications lists that would be great. (If you’re not on Windows 10, please say so.)
Oh, does the install date for your 2.0.0.7 match with your original install (mine does) or the re-install?