Each day there are 24 hours, no more no less. There are 7 days in a week too, so in total, there are 24 x 7 = 168 hours per week. If we divide 168 hours into 3 buckets of 'time', we will have 56 hours in one bucket, with a total of 3 such buckets. Let's look at the first red bucket. This is meant for sleep. If we have 8 hours of sleep per day over 7 days, we'll need 8 x 7 = 56  hours. This is exactly the number of hours we have in each of our bucket of time. So our first bucket of time is completely used up, just like that. Let's look at the second yellow bucket. This is meant for work. If we each work from 9am to 6pm, we'll work for a total of 9 hours a day. Plus travelling time ......