As far as I know the only time Google will not credit you for a click is if they think it's click fraud. Is that what you mean by discounting them? Or do you mean they changed the value of the click after reporting it as a certain amount?
Could you give a little more detail about what happened?
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What i think may have happened is someone clicked an advert, they paid you for it, then that same person clicked a load more, so they thought "Hmm, this person is clicking a lot of adverts" and decided not to pay you for any of them..
But as they have already paid you for the first click that seemed to be a legit click they deducted that payment when they reallised that person was clicking a lot of adverts..
the clicks can show up in your report then if at a later time google desides they where fradulent they can take them back it says in the tos if you read far enough