When you start a product, usage starts and is recorded. It stops when you close the product. Usage is reported by the number of days a product is used.
For example, Sophie launches AutoCAD at 7 pm on Monday evening. She closes AutoCAD at 5 pm on Tuesday. Her usage will be reported as one day of use on Monday (if she is using Flex tokens, she will only be charged the token rate for one day). No usage is counted on Tuesday as she closes the product in less than 24 hours. Also, if Sophie launches AutoCAD multiple times during that 24-hour period, her usage is still only counted in the Monday report.