Are you working with US FWS NWI data? If so then this document explaining the various classification & map codes is a must have.
A series of letter and number codes has been developed to adapt the national wetland classification system to map form. These alpha-numeric codes correspond to the classification nomenclature that best describes the habitat
Note: users of the Wetlands Mapper map service can obtain classification codes by using the Wetland Code Interpreter (yellow button) or users can optionally use this online database search form