Thanks for playing :) Sorry for confusing parts! Here's some clarification:
1. First, you should say how many single gems you think "you" have collected.
2. Then, the device will display both your claim and current enemy’s claim.
3. If the enemy claimed more than you, you get the chance to call their bluff. If you get it right there's a shotgun for you which will take two lives of the enemy.
4. Then you should choose the gem you think you collected the most
5. In the end your scores get calculated: Final Score = Your Claim × The Real Number of Your Selected Gem
6. Anyone with higher score gets a gun!