Counting-on strategy

Starting from a known quantity and counting only the added units. The strategy requires a link between the starting number and its represented quantity, rather than simply omitting words from a memorized sequence.

For addition of nonnegative natural numbers $a$ and $b$, start at $\max (a,b)$ and count $\min (a,b)$ further units. Commutativity guarantees the same sum while minimizing the increments among the two possible choices of starting addend.