You can enter values in the Null values, Distinct values and Average length fields on the Detail tab on your column property sheets, or obtain appropriate values from your database.
To obtain column statistics as part of your standard reverse engineering process, select the Statistics option in the Reverse Engineering dialog box (see Reverse Engineering from a Live Database).
To refresh the values in these fields for all a table's columns at any time, right-click the table symbol or its entry in the Browser and select Update Statistics. To update the column statistics for all the tables in a model, select (see Reverse Engineering Database Statistics).