Amplitude of fractal noise

[JeukHwang]

https://github.com/joshforisha/fractal-noise-js/blob/12bc7f877c5c135e589a6b01efca4c0835cdd58a/src/mod.ts#L51C1-L52C1

Why this is independent from persistence?

I thought the range of return value of makeCuboid is -amplitude ~ amplitude.
Isn't it?