getting error message with my code.

I am using the TLC5947 and I’m trying to simply change the dim level on each LED.
My code is giving an error message

Code:

#include <Adafruit_TLC5947.h>
#include <Arduino.h>
// How many boards do you have chained?
#define NUM_TLC5974 1

#define data   4
#define clock   5
#define latch   6
#define oe  -1  // set to -1 to not use the enable pin (its optional)

Adafruit_TLC5947 tlc = Adafruit_TLC5947(NUM_TLC5974, clock, data, latch);

void setup() {
  Serial.begin(9600);
  
  Serial.println("TLC5974 test");
  tlc.begin();
  if (oe >= 0) {
    pinMode(oe, OUTPUT);
    digitalWrite(oe, LOW);
  }
}
void loop(){
  tlc.setPWM(uint8_t chan, uint16_t pwm);
  tlc.setPWM(15,3000); //Ring L18
  tlc.setPWM(17,2500); //Ring L20
  tlc.setPWM(20,2800); //Ring L23
  tlc.setPWM(7,3500); //Ring L10
  tlc.write();
  }

Error message:

expected primary-expression before ‘chan’

Thank you in advance.

Don't include variable types in function calls.

And, you haven't defined any variables named 'chan' or 'pwm'.

Things are working, grateful for the help.