The brightness of this OLED can be adjusted by a resistor on PCB, you can find a resistor MARKed as 400K which a 910K resistor soldered, this resistor is the current controller for the pixels, replace it with lower value can make the panel brighter, but don't use too low value of it, that will shorten the OLED panel life rapidly.
Also, the brightness of OLED panel are vary depends on the manufacture and batch of production date, if you need same brightness in one order, please leave message with your payment to indicate it, then Digole will use same batch of panels to make your order.