said by Killa200:
XG-PON1 (10g assym) has a split ratio of up to 128:1 on fiber, making gbit downstream at max 12.8:1 and upstream 51.2:1
GPon (2.5 / 1.25) has a maximum split of 64
Cable docsis is unlimited within reason of hardware. Average of reason is ~256 max. A QAM 256 channel in a 6mhz slot is 38Mbps of usable bandwidth.
It highly varies, the numbers you're showing really aren't real world numbers. They're based on the receive sensitivities and theoretical splits that can happen and doesn't take into account insertion losses, cable losses, etc. So they're basing those claims on a 21 db spread between send/recieve sensitivities. A) it's not recommended to go right to the edges, B) it's highly improbable it would happen.
So if you get get it to 18 db, you'd get a max of 64 subs and withing 15, you'd get 32 which is much more likely and gives you some room for error.
as for cable, I was remembering the euro docsis specs which is 55 gross 50 usable.