When viewing the total average position in the Campaigns, Groups, or Dimensions tabs, the number is under 1.0.
This is caused by Product Listing Ads (PLAs), which have an average position of 0, but do receive impressions.
The average position calculation is weighted by impression count. The reason for this is to differentiate the performance of keywords with the same average position showing in the publisher over a certain period. The total average position is calculated by:
This is expected behavior, and it doesn't require a fix. However, when viewing the average position for a group of objects, it is best to make sure you don't have instances where there are impressions, but no average position (i.e. PLAs, content, etc.).