Issue #72 resolved
Starting GAP in a new session gives me this:
gap> B:=RandomBinaryRelationMonoid( 3, 3 ); <monoid with 3 generators> gap> Size(B); 16 gap> IsMonoid(B); true gap> iso:=IsomorphismTransformationSemigroup(B);; gap> T:=Range(iso); <transformation semigroup on 6 pts with 3 generators> gap> Size(T); 15 gap> IsMonoid(T); false
Obviously Size(T) should be 16. The size always seems to be one less, and is presumably due to missing the identity somehow.