This paper investigates an important algorithm that is used in both the Traffic-Flow Analysis and the Entity Flow-phase Analysis. These methods are similar to each other and can be used for the fast and approximate (performance) analysis of Information and Communication Technology (ICT) systems and Business Process (BP) systems. Both methods contain an algorithm for the spatial distribution of the traffic (or entities) in the system. It is shown how the error of the spatial distribution can be measured, and the effect of the so called size of routing unit parameter of two algorithms is investigated.