Clickhans - "Numbers" is an Apple format file which can only be opened in iWork Numbers on a Mac. It is similar to Excel. You will aslo find an Excel (.xls file) at the top of this post. If you download that it will run on a PC provided you have the Excel software.
I hope that helps.
When words become unclear, I shall focus with photographs. When images become inadequate, I shall be content with silence. - Ansel Adams