First one of this type of form that I've come across. Life Term Convicts from 1930s.
The "convict register" image does not have a column for file number.
In the attachment of the "next image", I presume we ignore the column indicated (which is obviously their file number) but not labelled at all. I know on the discussion page someone came across a column labelled "Number" which would be keyed as the file number, but this is different again.