For the file that you gave me, you can use the following:
{filenamebase:0,-13}
This will use the filenamebase variable, but stop at 13 characters from the end. The reason that you need to do this is because your file has a bunch of spaces before the real extension but after the fake extension. The variable above will leave off all of those spaces and the fake extension.
That said, since we don't know how the fake extension and spaces were added to the file, its entirely possible that your other files have a varying number of space characters after the fake extension, which will mean that variable that I've provided won't work for them and you might need to adjust -13 to some other number if there is a varying number of spaces.
