This means the amount of hours/time you have available to use doing productive activities like work, hobbies, socialising etc. The average person has 10-15 hours per day so has plenty of opportunity to do whatever it is that they need to do.
Useable hours is a term that is used to describe people with mental and or physical health difficulties to indicate how their lives differ from the average person. The amount varying by person and the conditions that they suffer from. The Neurodiverse Woman on Facebook – Cynthia Zuber, who is an American Autism advocate, says she only has 4 hours before she has to stop.
In Spoon theory this is simplified to having 12 spoons to account for each task that you need to do. Some times tasks can require more than one spoon and you can borrow spoons from the next day but that means you able to do less that day as a result. Spoon theory is an idea that is used to describe how much energy people with fibromyalgia use just doing basic tasks that we take for granted. It helps to communicate how difficult their lives are since we will never have such restrictions on our energy demands.