Seems to me that impressions in adsense and in webmaster tools do not mean the same thing. in adsense they seem to mean visitors to your page in webmaster tools how many times your page appeared in search results. what do you think? thanks.
Adsense has no connection with your webmaster tools. Google hasn't added a feature for this. You really need to read the webmaster tools help page to know what each feature/stat means. https://support.google.com/webmasters/?hl=en#topic=2370395