Lucent Technologies Ethereal - Manual (Page 124)

Value You may enter an appropriate value in the Value text box. The Value
will also indicate the type of value for the field name you have selected
(like character string).
Predefined values Some of the protocol fields have predefined values available, much like
enum's in C. If the selected protocol field has such values defined, you
can choose one of them here.
Range XXX - add an explanation here!
OK When you have built a satisfactory expression click OK and a filter
string will be built for you.
Cancel You can leave the Add Expression... dialog box without any effect by
clicking the Cancel
Working with captured packets
110