If $tau_1$, ..., $tau_n$ denote numbers, then the term {tt (* $tau_1 ldots tau_n$)} denotes the product of those numbers.
(Undefined (Arity *))
(Exists (?Y) (And (Integer ?Y) (Integer (* ?X ?Y)))) (<=> (Rational-Number ?X) (And (Real-Number ?X) (Exists (?Y) (And (Integer ?Y) (Integer (* ?X ?Y)))))) (Instance-Of (Arity *) Undefined)