Login to your website & from the site settings menu, navigate to:
Advertising > Edit Banner or Tile Ads
Click "edit" on the add you want to increase or decrease the display probability (weight) for.
You can see what the current probability of ads is set to prior to clicking "edit" - the default is "1" which means equal probability of being seen for each ad.
You will be on the "edit" tab.
Scroll down to the bottom of the screen.
Above the "Save" button, is a group of setting options.
Click on the "Weight" Tab
Click the drop-down under the word "Probability"
As you can see, there are multiple options to choose from.
The higher the number, the greater the odds the add will be seen. For example, a probability of
For example, a probability of "2" means that add is twice as likely to be seen as an ad with a probability of "1".
The lower the number, the less likely an ad is to be seen.
For example, an add with a probability of "1/2" is half as likely to be seen as an ad with a probability of "1"
Make sure to click "Save" to save any changes you have made.