In an A/B test, if you select Manual, you can specify the percentage of entrants you want to see in each experience. You can split the percentages evenly between all experiences, or specify higher or lower percentages for each experience. The total for all experiences must equal 100.
If you select Auto-allocate to best experience, most of the activity entrants will be automatically directed to the higher-performing experiences. Some visitors will be allocated to all experiences to maintain exploration of experiences and to recognize changes in performance trends.
If you select Auto-target to optimize, Target will use advanced machine learning algorithms to automatically target visitors with the best experience to maximize your goals.