Once per session
One per session refers to how actions in ConversionRuler are recorded, and can be useful when you want only a single action to be recorded for a particular visit. Be sure to understand what a Session means before you continue with this setting.
For example, if you wish to determine if a visitor just visits a page, but don't care how often they visit the page during their visit, you can use the Once per session setting to prevent duplicate actions from being recorded.
As well, based on how ConversionRuler records actions, this setting may prevent extra actions from being recorded on a page when it shouldn't be.
If you have a page which may have multiple different URLs associate with the same page, this setting may also help reduce duplicate actions.
Say we have a "Signup" action on our signup page. However, due to how the signup page works, many different URLs are generated on that page:
http://www.example.com/signup http://www.example.com/signup?zip=19063 http://www.example.com/signup?zip=19063&message=Please+enter+your+full+name.
Choosing "One per session" for this action would prevent the last two pages from recording a duplicate action.