The ABTest has two parts, one is traffic distribution and another is conversion. When you execute any test from client side, the server sends the variant applicable for this user as per the distribution you have created. Once client gets the variant name then you call goalAcheived when the user is really converted as per the app parameters.
The result is based on the goal achieved call. Suppose out of 100 users, 50 users called goal achieved for V1, 40 called for V2 and 10 called for V3 then the percentage of goal achieved will be 50% for V1, 40% for V2 and 10% for V3.
Let me know if you have any queries.