When you create a database update action you set Send Condition Parameters and Send Value Parameters. Send Condition Parameters tell the database which row of the table needs to be updated and the Send value parameters are the values with which you are updating the table.
The tricky part is when you use the action in a Connection object in a form. Both the Send Condition and the Send Value parameters will appear in Send parameters properties for the object. There are no return parameters, only send parameters. As a result, make sure that you don’t use the auto-complete feature when you are creating your action. Duplicate names in the two types of parameters will be confusing when you are using the action in a form.