Just curious.Why do you need to know? It's not like you can remove them and magically have a cfw or downgrade abilities
From reading several Tegra X1 spec sheets and information from several devs and the Tegra Shield, All I could conclude is ">512" where some numbers where even 4096, enough to blow one for every system update to come for its entire lifetime atleast..
Edit for extra information:
The fuses themselves are not conventional fuses like people think of, its basically a ROM chip thats writeable once.. so it could have 64 bytes worth of fuses, 128, 256, 512.. etc, I never could find the exact size.
Nintendo could release an update every day for years before all the fuses were blown. even if they did blow them all, updates could still be released without any downgrade protection.
It would be hilarious if Nintendo released a bugged update that blew all the fuses forcing them to release all future updates with no downgrade protection.