A single person will likely need 5-10 seconds to grab a manual from a shelf, place it in a banker's box, and move on to the next one.
If you look at the pictures like this one:
http://ascii.textfiles.com/wp-content/uploads/2015/08/IMG_69...
I could probably grab 25 or more of those at a time and set them in a box in 5 seconds, hence 5 per second. Getting the first ones out (because there is little "gap" to stuff hands into on the shelf) will be slower, but once the gap is made the whole pile easily comes out. This isn't about pulling one out at a time, spending another few seconds inspecting it, and then putting it in a box; it's about getting them off the shelves and out of the building ASAP.