It's the maximum event bytesize. iirc strfry defaults to 64kb. Not sure how many contacts that is without testing. I wrote a strfry-policies rule to limit most other kinds to something reasonable except for kind 3 so I could keep it at 64kb
Discussion
Oh yeah, forgot about that one. Strfry sets the default to 65536 bytes per event.
khatru is set to half a megabyte akchually
don't think there's many such relays actually running tho, based on how many bugs i've had to fix so far in my fork