In order to improve the possibilities of the designer (and also of the standard setter), a simplified Markov model is presented here, which is based on a probability concept for the description of operator activities on a machine. Thus, the risk reduction effects can be scaled probabilistically, at least in the order of magnitude of the powers of ten, since no decimal accuracy can be achieved here. A scaling of the probabilities is advantageous when it comes to the quantitative reliability requirements for safety functions according to ISO 13849-1 (2015). This is the case, for example, with a safe standstill of gravity-loaded vertical axes during operator activities in the working area of a machine, when it is necessary to manually eliminate unexpected problems during machine operation. A logarithmic scale is also used in ISO 13849-1. This paper explains for typical manual interventions how the quantitative requirements of ISO 13849-1 and supplementary safety regulations can be justified probabilistically. In addition, minor errors from the previous essay are corrected.