《明史·志·卷九》
取整数。各段实测到的太阳运行度数，与平均速度相减，余数就是积差。
各段实测日躔度数，与平行相较，以为积差。
Take the whole number. The measured number of the sun's running degree of each section, subtract it by the average speed, the remainder is the accumulated difference.