Loop Counter Issue I Can't Figure Out

Hi--

Not a noob here, I have a few years experience programming Arduinos, but the following behavior puzzles me. I can't figure it out.

int counter;

void setup(){
  Serial.begin(9600); 
}

void loop(){
    for (counter = 25; counter >0; counter--){         
      delay(100);
      Serial.println(counter);
    }   
    while(true){
    }   
}

and the output from the above is:
8
7
6
5
4
3
2
1

What happened to 25 through 17?

The Arduino is a Pro Micro 32U4, and that is 100 % of the code, no libraries or anything, and using a clean install of the Windows IDE 1.8.13, with no changes to the libraries or other dependencies.

Any thoughts about what's causing this?

Maybe the USB CDC serial connection wasn't ready yet? See Serial.IfSerial.

That was exactly it, thank you!

This is the first time I've used a 32U4, so thank you for your help!