This paper presents a case study on the implementation of IFPUG FPA and COSMIC software measurement methods for a small real-time system. The two methods were applied separately to measure the functional size of the same software. The main objective of this paper is to explore, through a case study, the issue of the measurement adequacy of each measurement method to capture the functional size of real-time software. For the practitioners, the real issue is that such a 'number' represent adequately the functional size. This number should take into consideration the particularities of specific real-time software and be sensitive to small variations of functionality.