Volcano Hellion's damage is capped at 255

[Pseudodude]

What is the expected behaviour of the card?

Volcano Hellion reads "When Volcano Hellion enters the battlefield, it deals an amount of damage of your choice to you and target creature." If the Hellion can be given lifelink in response to the trigger, it becomes desirable to choose a very large number to gain that much life when the trigger resolves (X to creature + X to controller - X to player -> gain of X).

What is the actual behaviour of the card?

On MTGO, the amount of damage is chosen by way of a text input with increment/decrement arrows, which accepts only digits as input. Entering a number between 0 and 255 inclusive works as expected, with Hellion dealing that much damage (and with lifelink, gaining back that much life). Numbers above 255, however, are truncated to the first two digits, e.g. 256 -> 25, 9999 -> 99.

Screenshot

The game log in this screenshot shows the results of two Hellions being reanimated with Whip of Erebos, the first with a damage input of 255 (correctly reported in the log), the second with an input of 256 (incorrectly interpreted as 25).

Please provide a list of affected cards
Affects: [Volcano Hellion]

Card Images