WhatConverts uses First-Click Attribution when reporting the marketing data for incoming leads. First-Click Attribution is a model where the first click that brings a user to a website is credited for the incoming lead.
Examples of First Click Attribution
A user visits your website on May 1st from a Google Organic search while doing research on a product you offer. After two weeks, on May 15, they come back to your site through a Facebook Remarketing campaign. They call one of your tracking numbers. That call will be credited as a Google Organic lead because that is how the user initially visited your site.
A user clicks on a text ad from Google Ads and land on a specific landing page you use for paid search traffic. They leave your site, but later that day come back after finding your company again from a Google Organic search. They make a call. In this scenario, the lead will be credited as a Google/CPC lead. All of the original marketing data that brought the user to your site will be credited for the lead. The Landing Page in your Lead Details will be the paid search landing page and the Lead Page will be the page they were on when they made the call.