Not that far.....don't have a screenshot right now. Pretty much less than 150Km...
Actually, I just figured it out that when the game reports a sinking ship (log book or map sunk ship icon), it won't count in the progress bar, and when it is not reported (it happens....), it is registered in the progress bar.
I have noticed that doing some ports raid......(don't ask me the name......but they are within the east British shipping lane)
