Don't worry, programmers don't always use the clearest language to express themselves.
1GB/hr sounds pretty slow to me, and like a pretty arbitrary figure. Surely it should depend on harddisk and CPU speed, as well as the content being indexed? Unless they're artificially limiting the indexing speed?
Harddrives are fast
today, and even a disk that's some years old should be able to read 50MB/s, and really a lot more. If we reduce that to 40MB/s to factor in disk fragmentation, and generally being pessimistic, that would still be 140GB/hr. RAM speed is measured in several GB/s (even for old DDR-1 RAM), but of course there's some CPU processing done and index file being written, but even if we pessimize by 10x, that would still be 14GB/hr
Of course these are just figures pulled more or less out of the blue air, but 1GB/hr seems weird to me.