Following [2], we present in this paper various number encodings and opera-tions over multisets. We obtain the most compact encoding and several other interestingencodings and study their properties using elements of combinatorics over multisets. Wealso construct P systems that implement their associated operations. We quantify the ef-fect of addingorderto a multiset thus obtaining a string, as going from encoding lengthsof the numbernin baseband time complexities of operations of the orderb√nto lengthsand complexities of orderlogbn.