Surprise! Someone else has used your worksheet, filled in some data, and made the number in cell C6 bold and red to highlight the fact that Peacock made the highest sale.
But that customer changed her mind, so the final sale was much smaller. You delete the original figure and type in the new number.
But the new number is still a bold red number! What gives here?
What's going on is that it's the cell that is formatted, not the data in the cell. So when you delete data that has special formatting, you also need to delete the formatting from the cell. Until you do, any data you enter in that cell will have the special formatting.
To remove formatting, select the cell and point to Clear on the Edit menu. The Formats command removes the format from the cell. Or you can click All to remove both the data and the formatting at the same time.