If you have multiple processors (like a laptop might have 4 or 8), then theoretically you can focus on 4-8 things at one time.
Likewise, I am wondering how many things the brain can "focus" on at one time simultaneously. That is, how many "processors" it has to process information sequentially. I am not sure if the brain even works similar to this, but wanted to ask anyways just in case.
For example, we might have a list of todos in the "back of our mind", a "few current todos" we are "actively" working on. Then at the same time we are minimally aware of the environment so we can hear surprising noises and react quickly to them (for example), so there is a processor available for emergencies (so to speak). So there is at least 2, the active one and the passive polling one. But if there is our "active" task, then what we have lingering in our thoughts might be a secondary focus/processor, so perhaps there a third processor.