On the ad's specific page in the Google Ads Transparency Center, if this data is available, an information icon will appear next to the data range of the number of times the ad was shown. The icon opens a dialog box that lists the individual ranges of the number of times the ad was shown on Google Maps, Google Play, Google Search, Google Shopping, and YouTube.
These individual ranges may not add up to the overall range of number of times the ad was shown. This is because the overall range could include older data and the ad could have been shown on other Google platforms not listed, like Gmail. Additionally, a range of 0-1k impressions could mean that the ad was not shown on that platform within the selected dates.
Google started tracking this information to be published on the Google Ads Transparency Center on Sep 4, 2023, so no impression ranges from before this date are published. In addition, for privacy reasons, impression ranges are published after a delay of 90 days.