6N1P conflicting heater/cathode voltage specs

I have two data sheets for the 6N1P, both Russian with English translations, which seem to give conflicting values for maximum heater to cathode voltages.

One specifies Ukh as +100V and -250V. As the k precedes the h I assume these are cathode voltages relative to the heater, so this spec says the cathode can be at most 100V positive with respect to the heater.

The other describes these parameters in words. It says: Voltage between cathode and heater:

- with heater at positive potential 100V
- with heater at negative potential 250V

I take this to mean the heater can be up to 100V above the cathode or 250V below it, which seems to me to be the exact opposite of what the other spec says.

So, which is right?

Cheers

Ian
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