FrameCount alarm, activating several times?

I’m making a fighting game that uses a frameCount alarm. It’s written like this:

if(StartUp1 >= 0){
	StartUp1 -= Time.frameCount;
}
if(StartUp1 < 0){
	StartUp1 = -0.1;
}

When I play it in the game, it works just fine the first time. Whenever I set the alarm again by entering a command, it runs out faster and faster each time. My theory is that the alarm activates several times over, but that problem doesn’t occur with deltaTime. Is there something that I’m missing? Possibly a special property of frameCount?

it runs out faster and faster each time

Of course it does, because Time.frameCount will increase by one each frame. What are you actually trying to do?

If you want an alarm that will fire after X frames, why not just count frames?

//set alarm
nextAlarmFrame = Time.frameCount + someNumber;

//check alarm
if (Time.frameCount > nextAlarmFrame) {
    ...
}