VMS Help CC, Messages, UNDERFLOW  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 Message        <Context> underflow occurs in evaluating the
                expression "<expression>".

 Description    A floating-point underflow occurred while evaluating
                a constant expression.  The value of the expression
                is undefined.

 User Action    Correct the floating-point constant expression.