Works for me on 4.2.2. Suggest you reproduce the problem on apex.oracle.com and post guest developer credentials here so we can take a look.
I can describe a little bit more about the issue (I'm working on recreating the issue on apex.oracle.com), what I have is a non database column, I create this column with a simple condition, but looks like from what I've been reading on this particular forum is that a non database column can't be formated with the number mask provided by the report attributes options.
One of my supervisors looked into the issue, we recreated the region and the issue was gone. Oddest thing ever I've ever come across.
Thank you so much for your time