To calculate the cushion, Shovel considers the available study time between the task start date and the deadline, the time it will take to complete the task, and other tasks that overlap with the task start date and the deadline. The best way to explain the cushion is with an example. Imagine that you have two tasks due on Friday; one in your history class and one in your engineering class. Let's also assume that you have no other tasks due this week.
Both tasks will take five hours to complete, and you plan to start working on both on Wednesday. So, in this example, the cushion of the history task will be calculated by taking all the available study time between Wednesday and the start of the history class on Friday, which is 16 hours, and subtracting the five hours it will take to complete the task. So, we're left with a cushion of 11 hours. Now let's look at the task due in your engineering class.
Shovel considers the sequence of your tasks based on their due dates. As the history task is due first, Shovel deducts the time you'll dedicate to it from the available study time for your engineering task. So, in effect, the starting point for the engineering task is the remaining cushion of the history task, which is 11 hours plus any additional time you pick up between the deadlines. In this case, there is a 40-minute study block between the history class and the engineering class. So, your total available study time is 11 hours and 40 minutes.
And just like with the history task, you have to subtract the time it will take to complete the engineering task, which is also five hours. So, in the end, you're left with a six-hour and 40-minute cushion for your engineering task. As you can see, even though the two tasks are due almost at the same time, the cushion for the later task is significantly smaller because we need to account for the time it will take to complete the previous task. I hope this makes sense. And now let's look at what you can do when your cushion is negative.