The Duration1 through Duration10 fields are custom fields that store any task, resource, or assignment duration (duration: The total span of active working time that is required to complete a task. This is generally the amount of working time from the start to finish of a task, as defined by the project and resource calendar.) information you want.
There are several categories of Duration1-10 fields.
Data Type Duration (duration field: A type of field whose content is expressed as a duration of time. Examples include the Work, Duration, and Delay fields. A duration field includes the duration unit, such as hour, day, or week.)
Duration1-10 (task fields)
Duration1-10 (resource fields)
Entry Type Calculated or entered (calculated or entered field: A field in which the value is determined by Project based on information in other fields. Information that you enter in the field yourself overrides calculated values.)
Best Uses Add one or more custom duration fields to a resource view when you want to enter custom resource duration information.
Example You want to see your list of resources in the context of their shortest and longest durations on your project. You add the Duration1 field to a resource view, name it "Total Duration," and enter the values of their rolled up assignments.
Remarks Values in the custom duration fields do not affect Project calculations. The default duration is "0 days."
You can create custom value lists, formulas, and graphical indicators for any of the custom duration fields. You can also create custom attributes or rename a custom duration field in the Custom Fields dialog box. Specifying a formula causes the field to become read-only.
You can copy the custom fields you create, along with their custom attributes, to other project files in the Organizer dialog box.
Duration1-10 (assignment fields)