Example of single value vs multiple value CCK fields?

Known Issues
Custom fields can't do anything intelligent with multiple value CCK fields. For now stick to single value fields in custom fields.

Can you better explain this statement or give an example in the Documentation?

I am giving a presentation at the Texas Master Naturalist Annual State Conference on how to use Drupal to track volunteer hours. The audience is there because they are not major computer users and need a step-by-step how to. As you can imagine, it's important that what I say works.

Node's custom fields: decimal (7,2)

• volunteer_hours - user enters 2.50
• travel_hours - user enters 1
• total_hours - computed field (3.50)

What is it here that prevents Views_Calc from performing an accurate SUM calculation?

Thank you for the volunteer time you donate to Drupal. As a volunteer myself, I know it is not always an easy thing to do.

Ashford