Override your studio fee for one class, or set a different rate for evenings and weekends.
Prerequisites
Scroll to "Class-Specific Fees" and "Fee Schedules".
Under "Class-Specific Fees" click "+ Add Override", pick the class, choose Percentage or Fixed Amount, enter the value and Save.
Under "Fee Schedules" click "+ Add Schedule", name it (for example "Weekend Rate"), tick the days it covers, set From and To, and choose the fee. Leave every day unchecked for it to apply every day.
Give a schedule a higher Priority number to make it win over another one that also matches.