YSK The three sets numbers on the inside arm of your eyeglasses are in millimeters for: lens width, nose bridge width, and temple length. Adjust size accordingly to your face and its features.
from /r/YouShouldKnow
YSK 眼镜内臂上的三组数字是以毫米为单位的：镜片宽度、鼻梁宽度和太阳穴长度。根据你的脸型和特征来调整尺寸。