This report continues the series of researches on the data set for peripheral blood oxygenation. Here we confirm the separation of the healthy adults into three subgroups by variabilities of oxygenation. Two new measures (descriptors) of variability are suggested, which correlate with the statistical analogs and Recurrence Ratios. These measures are handier in clinic praxis because of simpler computing comparing with Recurrence Ratios. We found the lower height of modes (i.e., of most probable oxygenation levels) and their higher variabilities for the riskiest subgroup concerning tor COVID-19..