Hi,
It looks like your cat probably hit F11, which creates a new worksheet for a chart like shown.
If you hit CTRL+Page Up or CTRL+Page Down on the keyboard it will switch back to one of the normal worksheets and you can click the FULL SCREEN button to display the worksheet tabs and delete the worksheet that was made.
Or if you prefer just send me a copy to
support@mycostpro.com and ill take care of that for you.
Thanks,
Scott