E-Spotting: adv statistics and log files

Experiencing differences between advertiser statistics and log files

[misciab]

I activated a PPC campaign with Espotting Italy two moths ago, and comparing the number of visits from Espotting+affiliates on my logs with the statistics of my advertiser account, I found very unusual data (for example, ratio 10 logs:200 espotting).

Any ideas of the possible reasons?
Thank you
Miriam