What is C.TRAIN.SCALES in /lib/model/utils/config.py??

Scale to use during training (can list multiple scales)
The scale is the pixel size of an image's shortest side
__C.TRAIN.SCALES = (800,)

Max pixel size of the longest side of a scaled input image
__C.TRAIN.MAX_SIZE = 1000

Trim size for input images to create minibatch
__C.TRAIN.TRIM_HEIGHT = 800
__C.TRAIN.TRIM_WIDTH = 800

I can't understand __C.TRAIN.SCALES mean.