What primarily dictates the asymptotic scaling measured by Big O notation?

Answer

The number of items, N

Big O notation is fundamentally concerned with the input size N, which dictates the number of steps taken. The magnitude of the data influences the constant factor (how long each step takes), but not the asymptotic scaling.

What primarily dictates the asymptotic scaling measured by Big O notation?
efficiencycomplexityalgorithmscalinginput size