Ho yeah you're right, it goes from 2 pages on the sides (which are the 1st and 2nd file) and then there are 4 pages and not 3 like it should. Also at the end, when there is the mention of the yellow door we start seeing the M-labs files.
Okay so I looked at it, when we arrive at the 4th file the one that always appear at the bottom right of the picture seems to be the next one and the ones on the side are those we have already read. So at the end there are 6 files on the left and with the on in the middle it amounts to the 7 total