@Becca A Nope, this is just the way it is until NetSuite finally gets around to updating their formatting (which I don't think they're going to do). It's actually a .xml (or something similar) file that's had the file extension changed to .xls so it'll automatically open in all versions of excel.

I had the very same question as I see in NS’s Help that “Supported Versions - Only XLS files are supported. XLSX files are not supported.” Why wouldn’t they update to xlsx? I think I will submit a request. And why is the font so teeny-tiny on the download?! Would you know of a way to change it?