Logging volunteer hours should not require an entry in all "Actual Duration" fields

When logging hours for a project/event, the system requires and entry in all fields for "Actual Duration." In actual practice, a volunteer coordinator may not have all the information for every volunteer at the same time or there may be more than one coordinator that has the appropriate information.

For example, I might be responsible for the check-in table and the volunteers that work with me there. As a volunteer coordinator, I need to get home and log that Suzy, Stan and Jill all were there at the table. But I may have no idea about Bill, Henry and Mary who were all at the refreshments table in another location entirely. I cannot log Suzy's time without logging Bill, Henry and Mary.

A more simple example is, I've logged all 15 of my volunteers but Henry is on the list. I don't remember if Henry was there or not but will ask him next week when I see him. I should be able to save the ones I know.