It kinda depends on the artist, doesn't it? And the implementation.damn dude how long does it take to just draw bigger boobs??
Some artists might draw bigger boobs in like 30 seconds (for 1 sprite) some might need more like 30 minutes., butit also depends on the implementation, does he only need to create the outline of the boobs since the color is automatically filled in through code? does he need to redraw the nipple too? And how many times does he have to redraw the bigger boobs?(THe number would be the amount of karryn sprities in the game, so probably quite a number) which would mean depending on the various possible scenarios it could go from 30 seconds to 30minutes per sprite. So a while.
The silver lining is that drawing bigger boobs is easier than drawing smaller boobs (why do you think all anime chicks have massive racks? Cuz it's easier that way!)