To modify you conversion attribution settings, go to Settings-> Attribution Settings.
You can then modify your settings as you'd like from this page.
Post-view vs. Post-click: Conversions are defined as post-view when they occur after your customer has loaded an ad from your Perfect Audience campaign on a web site. Likewise, they are defined as post-click when they occur after an ad has been clicked.
Conversion Lookback Windows indicate the number of days after a view or clicks occurs in which a conversion Lookback will still be attributed to your Perfect Audience campaign. With a 7-day post-click conversion window, for example, if someone clicks an ad and converts 7 days later, that will be counted as a conversion. If someone clicks and converts 8 days later, it will not.
Assisted Conversions are events when a user clicks or views an ad from one campaign but then later clicks or views an ad from another campaign and converts. In the situation above, normally the second campaign would be credited with a conversion and the first campaign would get nothing, but the reality is that the first campaign played some role in the user's path to conversion and that should be recognized in some way.
Attribution Rates indicate what percentage of post-view or post-click conversions you wish to count towards the CPA values in other parts of your dashboard. Example: a setting of "50%" for Post-View Attribution Rate tells the system to count 50% of the number of view conversions towards your CPA.
Note: If you don't wish to use Assisted Conversions, simply set the Post-Click and Post-View Assisted Conversion Windows to 0 days. That will also make the ACONV column in your dashboard stats disappear.