Customizing user allocation allows you to specify the percentage of visitors you want to assign for each variation in your test. Based on the percentage of visitors you allocate, you can further split the user percentage among the variations you create in your test. Customizing user allocation to each variation helps ensure that all your variations are adequately tested before you make a decision.
For example, you create a test and allocate 10 percent of your visitors to it. If the test has two variations, then you can allocate visitor percentage (100% in this example) for the test.
In the last step of the test creation process, select the Customize User Allocation for each Variation option under Advanced Options.
The user allocation for variations depends on the user percentage you have allocated for a test. By default, visitors are equally distributed among all variations.
Click the percentage icon to change the volume of users and then move the slider to increase or decrease user allocation.