After some testing in your Post Affiliate Pro (PAP) there are a bunch of clicks, impressions and sales. If you want to start from scratch, but do not want to reinstall your PAP, so you do not loose your current settings (banners, campaigns, etc..), you will need to erase all statistics data. Through the merchant panel you can remove sales easily, also removing clicks won't be a problem, but impressions and statistics data can not be removed through the merchant panel. That is possible only by manual modification of database data.
To remove all statistics data you have to truncate (empty) the following database tables:
qu_pap_clicks, qu_pap_cpmcommissions, qu_pap_impressions, qu_pap_impressions0, qu_pap_impressions1, qu_pap_impressions2, qu_pap_rawclicks, qu_pap_recurringcommissions, qu_pap_transactions, qu_pap_transactions_stats, qu_pap_transactions_stats_aff, qu_pap_visitoraffiliates, qu_pap_visits0, qu_pap_visits1, qu_pap_visits2
For versions before 4.4.x.x use this:
To remove all statistics data you have to truncate (empty) database tables - qu_pap_dailyclicks, qu_pap_monthlyclicks, qu_pap_dailyimpressions and qu_pap_monthlyimpressions