Please help me understand this sketch

Hello, I got a ARDUINO, PCA9685 SERVO MOTOR DRIVER 16 CHANEL MODULE.
I have this code from the tutortral: https://rootsaid.com/pca9685-servo-driver/

#include <Wire.h>
#include <Adafruit_PWMServoDriver.h>
Adafruit_PWMServoDriver pwm = Adafruit_PWMServoDriver();
#define MIN_PULSE_WIDTH 650
#define MAX_PULSE_WIDTH 2350
#define DEFAULT_PULSE_WIDTH 1500
#define FREQUENCY 50;
uint8_t servonum = 0;
void setup() 
{
Serial.begin(9600);
Serial.println("16 channel Servo test!");
pwm.begin();
pwm.setPWMFreq(FREQUENCY);
}
int pulseWidth(int angle)
{
int pulse_wide, analog_value;
pulse_wide = map(angle, 0, 180, MIN_PULSE_WIDTH, MAX_PULSE_WIDTH);
analog_value = int(float(pulse_wide) / 1000000 * FREQUENCY * 4096);
Serial.println(analog_value);
return analog_value;
}
void loop() {
pwm.setPWM(0, 0, pulseWidth(0));
delay(5000);
pwm.setPWM(0, 0, pulseWidth(140)); 
delay(5000);
pwm.setPWM(0, 0, pulseWidth(90));
delay(1000);
}

Perhaps I missed something, I am wondering where these two numbers come from?
#define MIN_PULSE_WIDTH 650
#define MAX_PULSE_WIDTH 2350
also I played with the FREQUENCY

How can I find the most reason numbers? Thanks.

Here is the documentation of that device.

#define FREQUENCY 50;Risky

Anatomy of a servo signal

#define MIN_PULSE_WIDTH 650
#define MAX_PULSE_WIDTH 2350

Servos are controlled with pulses nominally 1000 microseconds for 0 degrees and 2000 microseconds for 180 degrees. The actual microseconds full anticlockwise and clockwise limits vary from servo to servo as does the actual range of motion. One can find, experimentally, the microseconds for a particular servo's range of motion and insert those numbers into those constant to get the full range and also limit the travel to inside of the range.

also I played with the FREQUENCY

See the linked tutorial.