"Previoius definition of 'class TimerOne'" and creating PWM with Timer1

Using Arduino Programming Questions
22

Thank you for the help! It works now. Reading the signal on Pin 10 works. Now I have connected Pin 9 and Pin 6 by a cable. My current code looks like this:

#include "TimerOne.h"

unsigned long pwm_high = 0;
unsigned long current_t = 0;

volatile byte flag = LOW;

void setup()
{
  Serial.begin(9600);
	pinMode(10, OUTPUT);
	pinMode(9, OUTPUT);
	pinMode(6, INPUT);
	Timer1.initialize(50000); // initialize timer1, and set a 1/2 second period
	Timer1.pwm(9, 128);                // setup pwm on pin 9, 50% duty cycle
	Timer1.attachInterrupt(callback);
	sei();
}


void loop()
{
	Serial.print(digitalRead(6));
	/*if(flag == HIGH)
  {
	 Serial.print(millis());
	 Serial.print(F(": "));
	 Serial.println(digitalRead(10));
	 flag = LOW;
	 }*/
}

void callback()
{
	digitalWrite(10, !digitalRead(10));
	flag = HIGH;
	Serial.print("X");
}

And the output on my Serial Monitor like: 00011X11100000000000000000000000000000000000000000011X1110000

The goal was to actual see the PWM with duty cycle ~25%. But I am not sure how this works. When my timer1 overflows after 50ms so is the period of time for my pwm equal to 50ms right? And 25% of these 50ms should be on HIGH, but it turned out as wrong.