In this paper we discuss a specific result derived from a multiple case study. The case study involved implementation of IFPUG Function Point Analysis and COSMIC Functional Size Measurement methods in an innovative military software development project by different groups of experts. Application of these methods in a case that provides a number of size measurement challenges enabled us to observe significant improvement opportunities for the methodologies. In this paper, we depict the utilization of the entity generalization concept in two FSM methods and based on our observations we discuss the effects of different interpretations of the concept for measuring the software functional size.