Meaning of Item Notes Search Criteria

[armsys]

1. What are the meanings of the search options in the Comparison combobox for the Item Notes?
2. Is it supposed all info items contains the Item Notes attribute/field? Then, what's the purpose of "exists" comparison operator?
3. For "greater than", "greater than or equal to", "equal to"... does it compare number of chars inside the Item Notes? Or does it match a char string?