What is the impact of business hours on Task duration?

In tasks, the end time of a task is calculated by using the following fields: Start Date & Time and Duration; it also depends on the business hours of the user. 

For instance, consider that your business hours are from Monday to  Friday, from 9:00 AM to 5:00 PM. Your task starts on Wednesday at 3:00 PM and has a duration of 6 hours. Then, the end time of your task will be set to Thursday at 1:00 PM.