The game generates a number between 0 and 24, corresponding to these natures:

case "Hardy":
                    return 0;
                case "Lonely":
                    return 1;
                case "Brave":
                    return 2;
                case "Adamant":
                    return 3;
                case "Naughty":
                    return 4;
                case "Bold":
                    return 5;
                case "Docile":
                    return 6;
                case "Relaxed":
                    return 7;
                case "Impish":
                    return 8;
                case "Lax":
                    return 9;
                case "Timid":
                    return 10;
                case "Hasty":
                    return 11;
                case "Serious":
                    return 12;
                case "Jolly":
                    return 13;
                case "Naive":
                    return 14;
                case "Modest":
                    return 15;
                case "Mild":
                    return 16;
                case "Quiet":
                    return 17;
                case "Bashful":
                    return 18;
                case "Rash":
                    return 19;
                case "Calm":
                    return 20;
                case "Gentle":
                    return 21;
                case "Sassy":
                    return 22;
                case "Careful":
                    return 23;
                default:
                    return 24; (quirky)