QuickLook file associations
The information you are looking for is contained in each Quick Look plug-in's Info.plist file. This file is embedded in the Quick Look plug-in bundle: Contents/Info.plist

The number in the parentheses is the bundle version (CFBundleShortVersionString). This should be a unique identifier for the developer to determine the exact build of the plug-in; compare this to a marketing version of 1.1.

The qlmanage manual details how to see associations and the expanded help shows more options:

qlmanage -h


For details on how to add or change associated files, see Apple's Quick Look developer documentation. The associations are set out in the Info.plist file's CFBundleDocumentTypes section.

The MultiMarkdown Quick Look plug-in provides a useful example of the Info.plist settings.