I guess this version is (primarily) looking at the S/N, rather than specific # of rhinos pending.
I.e.: It changes whenever he updates the list for dropouts/no-shows/etc.
Before I had to have mine pushed back/paused, the tracking was as follows on my end:
28.10: 125 rhinos, S/N #0954
31.10 (after swap to algorithm): ~37 to go (~23 days), #0954
04.11, 06.11, and 11.11 had the same '~37 to go', #0954
18.11: ~8 to go (~5 days), #0856