Recorded: View-through conversions are recorded for the date of the associated impression.
Counted: Conversions are counted when there's a display impression on content. We count all conversions not associated with a click and attribute them back to the last impression in the last 30-days. Consequently, a single impression can be associated with multiple view-through conversion events.
Attributed: View-through reporting attribution follows the industry standard of last click, last impression attribution. This implies that the conversions are first credited to the last click, and if there's no click in the last 30-days, then they're credited to the last impression, preceding the conversion.
In Ad Exchange, a conversion that results from one ad view or click might not always be attributed to the proper campaign. Talk to your account team before using conversion tracking.