For it was pretty obvious when turning the frame upside down. Mark the middle of the frame with down tube as reference and measure the distance between this point and each BB face. If symetrical, I would put tge 3-4mm spacer on non drive side and and the 1-2 mm on drive side (if the preload ring is able to pressure on it.
Having said that, I am no bike mechanic, I go with what is logical to me… lol