The properties view of a part provides a way to display and set attribute values for a part. Every modifiable part has a properties or settings view that you can open by double-clicking on the part in the Composition Editor. Even if you don't provide a properties view, VA Smalltalk creates a default one for you. Opening the generic properties view for your timer part displays the following:

Note that for length, which expects an Integer value, the generic properties view provides an editable text field. For repeat, which expects a Boolean value, true and false radio buttons are provided.