When assigning a campaign, you have the option to set its pacing to Smooth Delivery. This tells AdButler to try its best to serve the ads in the campaign as evenly as possible over its duration, instead of simply trying to serve them as often as possible. For example, if a campaign has a quota of 30,000 impressions set over a period of 60 days, under Smooth Delivery, AdButler will try to serve the ads in the campaign only up to 500 times per day.
Because of this pacing, if you have multiple instances of the zone to which that campaign is assigned, Smooth Delivery may cause multiple instances of that zone to be served with the same ad item. This may happen if the campaign has yet to meet its quota.
To prevent this scenario, we recommend enabling Unique Delivery in the relevant zone. However, because Unique Delivery restricts the same ad from being served multiple times in the same page load, it might end up causing the opposite problem, i.e. leaving a zone instance blank.
That's why you must also set a default ad item or campaign on that zone alongside enabling Unique Delivery. Default ads bypass any restrictions or assignment details, including Unique Delivery.
For example, you have Campaigns A, B, and C assigned to the same zone. One or more campaigns have Smooth Delivery as their pacing.
Now let's say you placed three instances of that same zone on a webpage.
By default, the instances of the zone will be served as follows:
| Instance 1 |
| Ad from Campaign A |
| Instance 2 |
| Ad from Campaign B |
| Instance 3 |
| Ad from Campaign C |
Let's say Campaign A is behind on its daily quota. In that case, there's a chance that the same ad from Campaign A will be served multiple times on the page:
| Instance 1 |
| Ad from Campaign A |
| Instance 2 |
| Same as ad in Instance 1 |
| Instance 3 |
| Same as ad in Instance 1 |
If we try to offset Smooth Delivery by only turning on Unique Delivery, the situation could lead to the opposite problem:
| Instance 1 |
| Ad from Campaign A |
But if we turn on Unique Delivery and have a default ad item, the outcome would instead be:
| Instance 1 |
| Ad Item from Campaign A |
| Instance 2 |
| Default ad item |
| Instance 3 |
| Default ad item |
As you can see, this setup still leads to multiple ads on the same page, but at least it's the ad of your choice. If you want to ensure that each instance has a different ad, assign multiple ads to a campaign then assign that campaign as the default in the zone.
