Thank you for the image. It was very helpful. UEB does not make a distinction between acronyms and abbreviations when considering contraction usage, only between how they are pronounced. See UEB 10.12.1 and 10.12.2. So we need to decide if OFF would be pronounced as "off" or "O-F-F." Since this is about Office 2013, and "office" uses the OF contraction, I would pronounce it as "off" and use the OF contraction.