The Dormand–Prince method has seven stages, but it uses only six function evaluations per step because it has the "First Same As Last" (FSAL) property: the last stage is evaluated at the same point as the first stage of the next step.
The Dormand–Prince method has a total of seven stages. Nevertheless, it makes use of only six function evaluations at each step due to its inherent "First Same As Last" (FSAL) feature: the final stage shares an evaluation point with the initial stage of the subsequent phase.