I've installed Columbus 2.9.1, why do I see two Columbus Helper (64 bit) options on the Software Downloads page?
The two 64 bit options are actually for Mac OS 10.14 (Mojave) and Mac OS 10.15 (Catalina).
To differentiate between the two, hover your mouse cursor over the relevant link and in the bottom left hand corner of your browser window it should report the path to the download which includes information about the OS e.g.
ColumbusIP/file/download/Columbus/MacOSX_x86_64/Mojave_64bit/2.9.1/Columbus Helper for macOS Mojave.dmg
ColubsuIP/file/download/Columbus/MacOSX_x86_64/Catalina_64bit/2.9.1/Columbus Helper for macOS Catalina.dmg