For an hourly activity: In the Units field, enter the number of hours you spent performing the activity. You can enter parts of a unit in this field: for example, enter 1.5 if you performed 11/2 units of work.
For a non-hourly activity: In the Units field, enter the number of billing units you spent performing the activity. You can enter decimals in this field. Your non-hourly unit might be "day" or "week." You can enter an activity's unit of measurement in the Activity Information window.