Microsoft Excel's Data Validation tool lets you add a drop-down list to a cell based on existing data in a column. However, how this works depends on whether the source data is part of a formatted ...

The @ symbol can also appear in regular formulas outside of tables when Excel thinks you're trying to reference a single value from a range. If you see it pop up unexpectedly, it usually means Excel ...

I have used the Excel ... formula, meaning it was carried over from the formula entered in cell K2. If you wish to modify the formula for this customer, you will need to make those changes in cell K2.