<div></div>

div::after {
  font: 800 40px system-ui;
  content: counter(count);
  animation: counter 5s linear infinite alternate;
  counter-reset: count 0;
}

@keyframes counter {
  0% {
    counter-increment: count 0;
  }
  10% {
    counter-increment: count 1;
  }
  20% {
    counter-increment: count 2;
  }
  30% {
    counter-increment: count 3;
  }
  40% {
    counter-increment: count 4;
  }
  50% {
    counter-increment: count 5;
  }
  60% {
    counter-increment: count 6;
  }
  70% {
    counter-increment: count 7;
  }
  80% {
    counter-increment: count 8;
  }
  90% {
    counter-increment: count 9;
  }
  100% {
    counter-increment: count 10;
  }
}