This tab only appears for databases created with version 8.0.x of SQL Anywhere.
The Check Constraint tab of the Table property sheet has the following components:
Check constraint Lets you define conditions on a column or set of columns to make up the check constraint of the table. The check constraint restricts the values that can be entered in the column(s).
For example, to check that an employee's start date falls in a particular range, type:
CHECK ( StartDate BETWEEN '1983/06/27' AND CURRENT DATE )
See Using CHECK constraints on columns.