Thanks for the responses!
I think that indeed the Playtech casinos report higher click numbers than the actual numbers but the idea that clicks just differ for each promotion also sounds realistic. Therefore, I will try such an ad management package as is suggested. My only concern with this is performance. Isn’t the extra step of registering the click in my own db going to influence the loading time of the new page for my visitors (because the extra step has to be handled before actually leaving my site)?