A–The Dynamic Fit SRF parameters: summary data (points) and the fit from the relevant functions (lines) for the three Ca2+ handling conditions (purple–control; blue–CRU-CRU coupling enhancement; orange–SERCA upregulation and NCX downregulation model) against SR-Ca2+ for: i) probability of whole-cell SCRE; ii) initiation time corresponding to the separation point, ti; iii) the normalised cumulative frequency at this point, CFti,Sep = F(ti)|ti = ti,Sep; iv) the k parameter for F1(ti) and (v) for F2(ti); (vi) the median duration, MD. B–The General Dynamic SRF parameters: i) Illustration of the curve for probability of SCRE and its relation to the user defined parameters (CaSRthresdhold, CaSRP_range) and derived parameters (CaSRmin). ii) Illustration of the function form describing ti,Sep and median duration (MD) (purple line) and its relation to CaSRmin, CaSRmax, ti,Sepmin, ti,Sepmax, MDmin, MDmax, and how the range of the distributions varies with SR-Ca2+ (shaded regions) at two different non-linearity factors (Hwidth = 0.75, blue; = 2.5, orange).