How to: Modify Column Precision (Visual Database Tools)
The precision of a numeric column refers to the maximum number of digits used by the selected data type. For most data types, the column precision is automatically defined by the data type. You can change the column precision for the decimal and numeric data types if you want to redefine the column length.
The Precision property is not provided in the Column Properties tab of a column whose data type is not decimal or numeric.
To modify the precision of a columns data type
In Object Explorer, right-click the table with columns for which you want to change the scale and click Design.
The table opens in Table Designer.
Select the column for which you want to change the precision.
In Column Properties tab, click the grid cell for the Precision property and enter a value for the precision.
The Precision property applies to decimal and numeric types only.
The new precision value is assigned to the column in Table Designer after you click outside the grid cell or use the TAB key to move to another grid cell. It takes effect in the database when you save your changes in Table Designer.