Such as http://onlinebooks.library.upenn.edu/webbin/book/lookupid?key=olbp20910 Saying "translated from the 120th thousand." Or https://jscholarship.library.jhu.edu/handle/1774.2/30893 saying 40th thousand.

https://books.google.com/books?id=Xw4DAAAAQAAJ&pg=PA179&dq=thousand&hl=en&sa=X&ved=0ahUKEwiH0si13PPLAhWHOSYKHYyYDDgQ6AEIIDAB#v=onepage&q=thousand&f=false in the citations have a different thousand after each book citation.

What does the number mean, exactly?