Remember: you will want to start bringing the high temp in the brooder down 5* or so each week, eventually getting them acclimated to room / ambient temperature.
That is another thing that is easier with a really big brooder.
You can just leave the heat lamp alone in one end, and the chicks naturally spend less time there as they grow. They acclimate themselves to cooler temperatures by choosing to spend more time in the cool area. At some point, they are not using the heated area at all, and that's when you take the heat lamp out.
For chicks raised with a broody hen, she does not get cooler by a few degrees per week, and she never does heat the air around her. Chicks need the ability to warm up when cold, and the ability to move to a cool place. They do not need one "perfect" temperature everywhere.
I think charts like that were originally developed for conditions with hundreds or thousands of chicks, where it is simpler to heat the entire area to a single, consistent temperature rather than giving the chicks a choice. With small numbers, it is far easier for the keeper to just provide a range of temperatures (including LOTS of cool space), and let the chicks handle the details of exactly which temperature they spend time at.