When you get the Submarine in World 3, head directly 4 steps south of Karnark, and dive into the water. Now head south, you'll see a small hidden cave, enter it. There, you will find an old man in purple. Talk to him, if you say "yes", he will give you the number of.

Battles Fought
Monsters Slain
Average Experience
Treasures Gotten
Times Saved

This may not seem useful, but it actually kinda is, wether its using the Battles Fought and Monsters Slain to decide to either get the Chicken Knife or Brave Blade, or the know how much Treasure you have gotten.