Saturn2017

The Camera is inside a small room where people walk in and out

Hello; I have four CCTV video all have taken from the same security camera on four consecutive days with the same duration and time length; however, the avi file sizes vary almost 10% between the smallest and the largest ? Any explanation ? The Camera is inside a small room where people walk in and out I suspect an editing or tampering had taken place, but that needs to be supported