Changing qmake -query variables

I need to change all the variables under QT_SYSROOT as well as QT_INSTALL_CONFIGURATION to all be 32bit. I looked for documentation and found the qmake -set VARIABLE VALUE as a standard way of doing it however that just creates a new variable with that path instead of replacing the one under QT_SYSROOT. I attached a screenshot for clarification where you can see both versions of QT_INSTALL_PREFIX. Is there another way of doing this? Cheers!