How many impressions in 1 page load

[PowerUp]

If I have 2 leaderboards on 1 page, so how many impressions do I get when a visitor comes to my page and my page is loaded only 1 time?

1 impression because page is loaded 1 time?
2 impressions because of 2 ad units loaded?
8 impressions because 2 leaderboard x 4 ads?

[novice]

[webmasterworld.com...]

[Sweet Cognac]

2 impressions because of 2 ad units loaded

[greedy player]

ad impressions = per advertisement.
page impressions = all ads to 1 impression