The "006" refers to the "ticket stock" -- a term left over from the good old days of paper tickets. If you buy it on delta.com it will be on "006 stock" and should count for MQDs based on what DL has said.

If you buy it on klm.com with KLM flight numbers it will likely be on KLM's ticket stock (074?) -- from what Delta has said that won't count towards MQDs. If you buy from KLM.com and it is a Delta code share flight number then who knows -- should count but at this point it is not clear.