Our logic for A/B tests works as follows - when a User goes to a page where an Experience with an A/B test is running, they are being shown with one of the Offers or Templates from the A/B test. The A/B test is sticky (it works based on a cookie being set in the user's browser), which means that visitors will be shown with the same A/B test variant until the A/B test ends or the A/B test proportions are changed.
However, when the user clears their cookies or changes the device, the A/B test branch is being assigned again (as if they were a new user). So, there is a chance that the user will be shown with a different branch. More information about how to set up an A/B test is available here.