It got like that by choosing Window/New Window.

Close one of the windows and save the file.

In article ,
Need Advice <Need wrote:

When I open my excel document it opens the same document twice, after the
file name it as :1 and the 2nd document (same as the 1st) has :2 after the
file name. You can view each of these files by clicking on Windows and
selecting the other document. I'm not sure how my file got like this, how do
I undo it?