Data was multiplied then forced on top of the original on Numbers

Here is a single table on a canvas:

I intentionally duplicated the table:

If you want to unselect both tables, click outside the tables on the background (the canvas). Places where you should click in this example are denoted by stars that I added:

Now single click any cell in the top that is on top:

Now you can see only one set of table controls are enabled.

single click the "bullseye" at the top left, then type delete:

This is not an Apple problem. It is an accidental user error. I have made the exact same error. the canvas (the background is any area that is not where objects reside.

You accidentally duplicated a TABLE. I suggested using the menu for the SHEET to choose the extra table from the SHEETs menu.

you accidentally duplicated the table.

Choose from the menu for the sheet tables until the "extra" on is highlighted

Then type the delete key to remove that table.

You may also try using the menu item "Edit > Undo" until the mistake is cleared

I am asking the moderators to remove the image from your post since it has peoples names and some numbers. In the future, I suggest posting the image with a solid-filled rectangle over most of the identifying text. The screenshot was very helpful.