It sounds like your Excel file may have hidden data or formatting that is still taking up space even though you have deleted all visible cells. Here are a few steps you can take to try and reduce the file size:

1. Remove hidden rows and columns: Sometimes, even if you have deleted the cells in a row or column, the row or column itself may still be hidden and taking up space. To check for hidden rows and columns, select the entire sheet by clicking the box at the top left corner of the sheet (above row 1 and to the left of column A), then right-click and choose "Unhide". If there are any hidden rows or columns, they will appear and you can delete them.
   
2. Clear formatting: If there is any formatting applied to the cells, such as borders, shading, or font styles, this can also take up space in the file. To clear all formatting, select all cells by clicking the box at the top left corner of the sheet, then go to the Home tab and click the "Clear" button in the Editing group. Choose "Clear Formats" to remove all formatting.
   
3. Check for objects: If there are any objects in the sheet, such as charts, shapes, or images, these can also take up space. To check for objects, go to the Home tab and click the "Find & Select" button in the Editing group, then choose "Go To Special". In the dialog box, choose "Objects" and click "OK". Any objects in the sheet will be selected, and you can delete them.
   
4. Save as a new file: If none of the above steps work, you can try saving the file as a new file with a different name. Sometimes, Excel files can become corrupted or have hidden data that cannot be removed, and saving as a new file can help to reduce the size.

I hope these steps help you to reduce the size of your Excel file.