After knowing that marvellous cheat for fishing joy, i was trying to gain as many coins as i could in order to see what will happen after my coins reach the max of the five-digit counter.
It's not long before the counter doubled. My fingers were actually aching (on the verge of developing acute flexor tendinitis) but i was so near to reaching the maximum.
Though 100,000 was not reflected visually, i realised the system actually stored more than that amount. I shot many 7-coin nets and the counter only started decreasing after an hour or so.
For the cheat on fishing joy to generate coins easily, please click here. Do note that it might not work for jailbreak iphones.