Payout Rate question

Hello,

I have a question regarding payout rates.
According to your statement I earn at leat 0.50 for
every 1000 visitors.
I have a bit more than 39k views and only 18$ earnings, whereas it should be at least 19.50.
My tracking tells me that I haven't got a lot of double IPs (less than 3000 that would explain the missing 1.50 anyways, although I highly doubt all my traffic is coming just from 0.50 sites) and
as far as I know, if there are double IPs outside of a 24 hour window, they will be counted fully each. Is this right?

Perhaps you could clarify this for me as I have to consider cancel using your service otherwise.

Thanks a lot.