If you win 100% of impressions bid (i.e., win rate equals 100%), you have not necessarily reached the maximum number of impressions available overall.
The 'Impressions Won' column is displaying the amount of impressions bid that you have won. This is determined largely by your bid CPM.
If you alter your targeting criteria (e.g., raise your CPM bid, add more sites, add more ad dimensions, or change frequency cap), you may have the opportunity to win additional impressions.
There are several things you can do to increase the number of impressions that your campaign is buying:
- Consider raising the bid to compete for more of the site’s available volume.
- Ensure that you are not hitting your campaign budget -- if so, raise it.
- Raising your frequency cap will also ensure you win more impressions (showing ads more frequently to a user can result in higher CTR, or more visibility at the very least.)
- Ensure you are using every ad size that the site has available.
- Consider adding more sites to your campaign.
- Loosen location targeting (choose a larger region)
- Loosen device/browser/OS targeting
- Open up day parting, if enabled
- If it's a contextual or audience campaign, try adding more segments, categories or reducing the "relevance" required (classic UI only)
- Turn off "Deliver the budget evenly throughout the day". If the targeting settings constrain the campaign to a very narrow number of bid opportunities, its important to be bidding on every opportunity possible.