<div></div>

@property --num {
  syntax: "<integer>";
  initial-value: 3 * 26 * 26 + 19 * 26 + 19;
  inherits: false;
}

div {
  transition: --num 0.25s;
  counter-set: num var(--num);
  font: 800 40px system-ui;
  padding: 2rem;
}
div::after {
  content: counter(num, lower-alpha);
}
div:hover {
  --num: #{25 * 26 * 26 + 5 * 26 + 19};
}