Unfortunately, the bookcase in question was my big "scifi" bookcase, which had books in some cases quadrupled up on each shelf. Also, a lot of the books on that shelf date back to the 60's and it seems that folks didn't start using ISBN numbers until the 70's, which means that I either have to scroll through a lot of editions, or manually enter the info. It is, needless to say, taking me a LOT longer than the "newer shelves" did!
I also had to figure how to "log in" these with a system that would work with the others, given the "overloaded" nature of the shelves, so I've gone to something like C5-S4a-B01, with "a" being the base row of books in back, "b" being the row of books in back on top of "a", "c" being the row of books in front of "a", and "d" being either the row on top of row "c". Yes, my neuroses are in full flower!