When we Mass Update a User Defined Field, we have the option to remove values from the accounts or journal entries in the query. Some User Defined Fields have multiple values, though. For example, we may have a User Defined Field that tracks a constituent's favorite color and we can mark as many check boxes as we'd like.
If we opt to remove a value from a User Defined Field using Mass Update, this process will only remove that selected value from the constituent's account. In the above example, we could have a constituent who has red, blue, and green marked on their account. If we run a Mass Update to remove green from the account, only the green value will be removed; red and blue will remain marked on the constituent's account.