I am wondering about the actual way impressions are counted. Google defines "impressions" as the "number of times your ad is shown."
This definition leads me to believe that if your ad is not on the first page of the SERP but only accessed via the "More Sponsored Links" page, then it would not count as an impression if the user does not click on that link.
It's really interesting to me that the 'More Sponsored Links' section has come up several times today - with the last time being weeks ago, if not more. (If I recall correctly, which is question today, actually.)
The More Sponsored Links results are actually something of a 'special case' as explained on this page from the AdWords Help Center.
Since the page is relatively short, let me just quote it - with some bonus italics added by me:
What happens when I click 'More Sponsored Links' on a Google search results page?
Clicking More Sponsored Links on a Google search results page brings you to our Ad Search feature. Ad Search allows users to search through our active ad inventory for relevant ads and provides advertisers with more opportunities to reach their target audience.*
As an extension of Google's search results, these ads are ranked differently from competing AdWords ads. Clicks and impressions accrued by these ads aren't reported in your account and their performance has no influence on your account or how our system calculates your keywords' Quality Scores. Advertisers are not charged for any clicks that result from these ads.
Please note that because ads are shown based on a user's search terms (keywords), they are not filtered for language preferences. This means that users may see ads in languages other than their own.
*Ads displayed include those that have already met the daily budget for that day, ensuring that all ads have the same opportunity for exposure. This also ensures that users have comprehensive results for their query.