The author of the book Hyperfocus used the term “Attentional Space” to refer to the amount of real estate available in your working memory. This is, according to him, about 4 things on average instead of 7, per ~7 - The Limit of Simultaneous Info. He suggested auditing your attentional space from time to time to check if your attention aligns with your intention.
Apparently your attentional space shrinks and grows in response to your circumstances. If you’re tired due to low energy or a Sleep Detriment, it shrinks. If you meditate, it can expand.
You are most productive when the task at hand fills your attentional space, and your attentional space is large enough to accommodate the task.