The Enumerations tab is only available for simple type restrictions. It allows you to enter a set of acceptable values for the simple type restriction.
Select F (for Fixed) at the end of a row if you want to prevent the modification of a value.
For example: the meetings simple type, based on the xs:gMonthDay data type, is restricted to the following dates: 01/20, 03/20, 05/20 and 07/20.
Generated schema: