The information about Dragon descriptors can be found at book of R.Todeschini and V.Consonni: "Molecular Descriptors for Chemoinformatics", (2 volumes), WILEY-VCH,Weinheim (Germany) 2009, 1257 pp.
A brief description of them can be also found at Virtual Computational Chemistry Laboratory as well as at Dragon User Manual
N.B.! These descriptors can be only used for model development on OCHEM web site and cannot be exported.