A finite map lesson begins with a seed, a rule, and checked states. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
A map is a rule plus a seed
The seed is 0 and the checked rule sends it to one quarter.
x1=2x0+41=41
The ledger stops at the pinned depth
The four displayed states are the seed, one quarter, three eighths, and seven sixteenths.