VWO tracks the 'visit to a page' goal as soon as a visitor arrives on the page, but the 'revenue conversion' goal is triggered only when the Document Object Model (DOM) is ready. If a visitor leaves the page before the DOM is ready, VWO records only the 'visit to a page' goal. This explains why the numbers of conversions recorded for the two goals may not be the same.
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NOTE: If your workspace is enabled with Data360, you will be able to use Metrics instead of Goals for tracking standard and custom events on your website. However, if you are encountering a similar scenario, the explanation provided in this article will still stand applicable.