Pyrex:
I am not sure if this should be done on the library side or the Arduino code side.
Haven't looked at the library in great detail (and the "manual" for the modules appears to be obscured from download), but it certainly does not look as if it would contain any code relevant to this purpose. Nor could it, as it is only called when you need to change the number displayed.
In particular, this is something that needs to be done from time to time in concert with whatever main program you are developing, something like a "screen saver" (which is in fact, exactly what it is) which kicks in when nothing is happening or in the case of a clock, as each minute passes. So it is clearly something you put in your main code, and should be pretty straightforward.
Something such as: take the current digit displayed, increment it and display that; wait 50 ms, repeat the increments and waits until the number would be what was first displayed and then display the new digit.