Editing an unlocked cell within a table on a protected worksheet

I have the following message pop up whenever I go to edit a cell on a protected worksheet. The cells are 'unlocked', and they still let me enter/delete data in them, but the message pops up.

"The cell or chart that you are trying to change is protected and therefore read-only.
To modify a protected cell or chart, first remove protection using the Unprotect Sheet command....."

Just can't understand why it pops up on the unlocked cells and then lets me edit them anyway.

Road Signs Worksheet.xlsm

The cells with the white background are the unlocked cells. If you try to delete either of the numbers shown in these cells, the error pops up (eventhough they are unlocked).