True number of training samples for the training set in VOC 2007

[Dai1029]

In fact, I looked meanwhile other literature and most of the literature wrote using 2072 images from voc 2007, but in the code you provided, I could only get 1622 images that could be used for training (after excluding images that appear to be unseen classes).

I'm wondering if there are any that I need to be aware of additionally. Looking forward to your reply. Thanks.