There is not such standard field as DNS in Marketo. Marketo has "unsubscribed", "Black List" and "Marketing suspended" and "email invalid"
These are filtered out at the very moment Marketo sends the email.
Yet, in a Batch smart campaign, in the schedule tab, you would have a count of the number of leads that will be targeted by the campaign and another count of the number of leads that cannot be sent en email.
The number shown to you on the Schedule tab is just an estimate of what would hold true if you ran it right now but that number could change if you don't have it scheduled to run till a later time or date.
Hey Elizabeth, to answer the exact questions that you've laid out, criteria in your smart campaign are checked by Marketo at the time that the campaign is run. The one exception to this is if you're using the Email program head start that allows you to pre-process the send so that it goes out at an exact time.
The "set to affect around x leads" does reflect the criteria in your smart list, but obviously something can change between when that approximate number is populated, and when you actually run the campaign. Also, if someone has hit their communication limits they will be included from the "set to affect" number, but excluded from your actual send.