Regarding synthetic training dataset generation

Hi, The "VOC2012_224_train_png.txt" file lists 15,287 images and the training dataset consists of half of 15,287 i.e. 7,643 images. Is the split for the reflection and transmission layer images random? Can I split the 15,287 images into two equal sets randomly : transmission layer and reflection layer, and go on to combine one image from each set to get 7,643 images containing reflection ? 