Differences for 'V' and 'DV' of a signature field

I have a questions regarding the signature dictionary (PDF 1.4 since PDF/A).

According to the spec V and DV entries of a field dictionary (of a signature field) both contain signature dictionaries.

According to the signature dictionary spec the following attributes are required:

- Filter

- ByteRange

- Contents

-> If i add an V entry those attributes have to be filled (at the time of signing the document)

But what about the DV entry?

Quote from the spec:

"The DV (default value) entry in the field dictionary may specify a signature dictionary for an unsigned field that is preloaded with default values for some
entries."

-> Thus i don't need to prefill those upper three? At the time of the prefilling one can't fill those three because the information is not available...

Thanks for helping,

ToM