Actual Allocation on User Utilization will reflect the logged hours which fall within the planned start and completion dates of the task.
Planned Start Date - 06/08/2016
Planned End Date - 06/09/2016
If an hour is logged for 06/08/2016 the system will show Actual Allocation % for the user. However if you log an hour outside the date range (for example, 06/05/2016) the system won't consider it as an Actual Allocation.