We are talking about time estimates for delivery purposes. We need to know when the tasks or activities will be done not how long it will actually take. You might need 10 hours of actual work but the task won't be completed for 40 hours because you have other things to do. For your time estimate you would use 40 hours. In your cost estimate you would use only the 10 hours of actual work.
Many people fail to distinguish between the two types of estimates.
In the previous article, I showed a form to collect needed project information. This is a copy of that form. It could be on paper, a database or any other method you chose as long as you have the information. The next to last line is about your time estimate. Once, because if you did it better than that, the new time is your best.