A 20 A circuit in a home can take 20 A of Table C9 contributions, which is 20 single 10 A socket‑outlets. AS/NZS 3000:2018 Table C9 gives each point a contribution. The tool checks that the sum stays within the circuit-breaker rating.
The count
In a domestic installation, one 10 A socket‑outlet counts 1 A. A 21st socket‑outlet takes the sum to 21 A, over the rating, and the tool reports a fail.
Other installations
A non‑domestic installation counts more per point. There, 20 socket‑outlets come to 40 A, and 10 of them fill the circuit at 20 A.
The count is a loading rule, not a cable size. Size the cable for the circuit separately.
See also: What size cable for power points in NZ? and Maximum demand and diversity.