Experience and observations often underlie some widely used numerical characteristics. The problem is in the extent to which such characteristics are optimal. The paper presents results of theoretical analysis of the most frequently used numerical characteristics regarding the number of classes in classification systems, of the base of the number system, and of the level of confidence in the various estimates. Conceptions of informational optimality, harmony and balance were used as criteria in the analysis. The study was also aimed at determining the allowable deviation from the optimal values (mathematical constants) in the identification of the manifestation of harmony, balance and optimality. The predominance of manifestation of mathematical harmony in nature and human activity has been explained using the estimation of optimization reliability.