Hi guys, please those that own adsense account I need some explanation on how adsense arrives at their estimated earnings.

Looks like they don't pay for impression? I noticed in my account its only the CPC that makes up the estimated earning.
I have over 1,000 impression, I thought this is suppose to be around 1 dollar alone then if you add maybe 0.4 dollars from cpc earning your estimated earning will then be like 1.5.
but my estimated earning is showing only CPC as estimated earning

Isn't this how it works?