Based on the project created in Wix: Using Patch Creation Properties - Small Update,

Following changes are made to make a minor upgrade:

1. Change Product Version.

2. Add MinorUpdateTargetRTM="1" under PatchMetadata node.

Details see attachment: SetupWix.7z

Reference:

http://windows-installer-xml-wix-toolset.687559.n2.nabble.com/Creating-multiple-Minor-Updates-td7586073.html