Two measurements of one ordered genealogy
Regular and Cumulative chronology can be read as two measurements of the same ordered genealogical rows. Regular chronology accumulates the effective interval from one birth to the next; Cumulative chronology accumulates the selected lifespan of each person. For a compatible row, begetting age plus remaining years equals lifespan. Moving years between the two parts can therefore change the Regular chain while leaving the Cumulative contribution unchanged. Adam's 130 + 800 and 230 + 700 both preserve 930.
This local distinction generates a whole comparison field. If G is the difference between corresponding Cumulative and Regular coordinates, each adjacent change in G equals the lifespan minus the effective Regular interval. One terminal placement and the ordered row contributions reconstruct every intermediate comparison. The rule works across the complete MT, LXX, and SP source profiles, provided their inserted rows and counting conventions remain explicit.
The SP cap adds a mechanism that changes the lifespan itself. Birth distances determine which ancestral lives encounter the Flood boundary, and the resulting reductions pass into the Cumulative field by the same ordered accumulation. This explains why shared births need not imply shared Cumulative dates: the aligned Noah-to-Abraham birth path of SP-with-Cainan and native LXX still carries different lifespan measurements.
Sources: Research Strategy §3.2, §5, Stages B and G; File18 §§2.1.3–2.2, §§3.1–3.2, §4.1, §§6A–6D; File09 §§0.3–0.4.
Research record: C733–C748, C787–C788, C954–C956, C972–C973.