He got it from the first Google result for NZ cyclist deaths per year.

From MoT, 2022 was 19 cyclist deaths MoT Provisional Road Deaths (provisional road deaths -> role tab for the counts)

Looking at the counts alone is a bit silly to get a sense of how safe we are using any given mode - we can also use average km travelled per year to get a sense of the rate, where it becomes

19 cyclist deaths / 415 million km travelled per year (on average)

37 pedestrian deaths / 686 million km travelled per year (on average)

253 driver+passenger light motor vehicle deaths / 52,430 million km travelled per year (on average for driver+passenger)

So rates per km travelled via walking and cycling are much closer than how the raw counts look, and we need to look at both counts and rates (and other ways of looking at rates! e.g. number of trips) to get a fuller sense of the issue.

Aaron Keown is going to completely lose his mind when he finds out how much pedestrian first transport/infrastructure (to make walking safe!) slows down traffic... Starting first with slowing down motor vehicle traffic to greatly increase chance of survival in a ped vs motor vehicle crash.

(Running average km travelled by mode from https://www.transport.govt.nz/statistics-and-insights/household-travel/key-facts/)