Changing one-column strip height complements the row-length projection scan. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Two stacked cells give column sum six
A one-column strip with cells 2 and 4 has column sum 6.
2+4=6
Three stacked cells give column sum twelve
Adding cell 6 raises the column projection to 12.
2+4+6=12
Four stacked cells give column sum twenty
The four-cell strip adds 8 and the projection becomes 20. Three rows show height as the source factor.