Those ranges are fine.
They are non limiting for any light level.
However, if you have less light, say you have 1.5w/gal of T5's, you can easily do with 1/2 that amount.

The goal is to target a level, not keep it precisely at that level the entire time. If it goes a little one way or the other, it should not be a big deal.

If you keep up on water changes and a simple dosing routine that can be consistent with, then this should not pose a problem.

Light drives growth rates which in turn drives uptake of CO2, which in turn drives N uptake and so on down the line.

Regards,
Tom Barr