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I assume that there are site-targeted ads on the page, but even with that in mind, I don't quite understand those stats. Is Google making fun of me?
Also Google could treat those 2 clicks as invalid.
It won't help you much, but with only 100 impressions any stats are going to produce pretty unusual, highly variable and generally meaningless data.
It's highly unlikely that you are showing any site targeted ads with the number of impressions you indicate
I believe you need your number of clicks to be in the hundreds if not thousands at least before you can really start to get any useful data from the stats.
Work on building content and links to get your traffic up.
However it appears that Google do their calculations using fractions of cents (maybe hundredths). As the ECPM is calculated to an accuracy greater than just dollars and cents would allow.
So although it may appear as 0 cents in the stats it is actually 0.x cents. And those fractions of cents do add up to make whole cents when the total is calculated.
What stumps me now is how different the eCPMs of the two ad types are: The eCPM of the site-targeted ads should be relatively stable, regardless of the low number of impressions, right? The eCPM of the contextual ads looks pretty stable after about 100000 impressions. Why do the site-targeting adword customers need to pay several times more eCPM to get just the few impressions in?
Different ads appear on your pages - what each ad pays can vary enormously.
For meaningful stats about your average earnings per click you need 100's of Clicks - the number of impressions is irrelevant.
In addition, for very low values of earnings, I would expect that rounding errors and currency variations have a disproportionate affect.