This only happens if it is implemented as percentage already but simply not labelled it accordingly (which seems to be the case here).
However, what happens to the bar depends on how it is implemented, or rather on what it
expects (i.e., percentage values or arbitrary numbers) and what it
gets (i.e., arbitrary numbers or percentage values), and how it deals with out of range data (usually not at all

or by cutting off at maximum value). It may go over the outline (to be cut off somewhere or go past the edge of the screen, whereever something is drawn on top of it), it may stay at 100 until your health drops below, or not be displayed at all until you reach 100 or lower, or any combination.

However, I have seen these things actually happen too often to find them funny...
