A click through did not make money?

Last night I was checking my AdSense stats, and one of my channels had 3 clicks, with total earning of $0.20
THis morning, the stats showed 4 clicks for that channel, but the total earning was still $0.20
Did one advertiser get a $0 ad? or did google 'forget' to credit me?

 

Sometime there is some delay in reporting... Might be that.

 

Few of the advertisers pay after Each 5 clicks

 

So only if that ad is showed again on my site, and is clicked on 4 more times do I get paid? or do they pay for every 5 clicks anywhere in the web, and when their ads get clicked elsewhere i'll get my money?

 

sometimes you will get one click with no money, sometimes you will get money with no click. these are isolated cases and you should see how you make by taking the average. google doesn;t reveal their secret on how they pay the publishers

 

sometimes it may be an invalid click.

 

Maybe they have clicked a public service ad?

 

I've experienced this before as well...it's a bit annoying. I think the 5 clicks thing sounds the most likely explanation.