When you set Auto-payments every to any option other than starting on the sale date, clients will be billed the full price of the membership on the day that they purchase the membership but will not have access to the membership until the date specified in the Auto-payments every selection.
For example, a membership has a price of $50 and has Auto-payments every set to starting on the 1st of the month. If a client purchases this membership on April 26, they will have to pay the $50 membership fee for the month of April but will not have access to the membership until May 1. They will be billed for the next membership period on June 1.
If you want to prorate the price of a membership, you can do so at the point of sale. For more information, see Prorating memberships. You can also change the start date of a membership at the point of sale. For more information, see Setting a membership start date from the shopping cart.