Office X 10.1.3 is an incremental update to 10.1.2 combined updater. You must the install 10.1.2 update before you can apply the 10.1.3 updater. (Since 10.1.3 applies only to French and Italian proofing tools, I never bothered with that update. 10.1.2 is very much worth having. But if 10.1.2 wasn't installed already, the 10.1.3 updater might give such a message (much as Apple's updates simply refuse to show your hard disk if the OS on it doesn't meet prerequisites.)
The default location for Office X is /Applications/Microsoft Office X.