Don't feel bad, I got 20 clicks one day and NO money! I'd never gotten 20 clicks in a day before, so I figured it was just some friend I sent the link to trying to help me out.
I had also that earning when I first started to use adsense but later on I got big amount on per click.
It's too bad, I don't know there is such a low payment. But be patient, things can be tough at the first time
It could have been a survey ad, I had that one day and it was an advert asking people to vote on best player and only paid like 1cent a click.
Could it be in a low paying niche.i have a few sites that i made just after getting started.never did any keyword work (tattoo niche) i get 100s of 1 and 2 cent clicks.
Or could be because of MFA ads being displayed. Like for the past few days I noticed that one of my website was generating 10-15 clicks daily but total earning per day was $0.5 or less. I looked at it and found a few of MFA ads being displayed which I promptly removed by putting them in competitive ad filter.
It is most likely that google has determined that most of your clicks are invalid and therefore, you are only credited a certain amount. If constantly you encounter such figure, it's time to report to google.