<p class="">font-size 10pxです。</p>

<p class="adjust-font-size">font-size 10pxをtransform scale(0.8)で調整した例です。</p>
p {
  font-size: 10px;
}
.adjust-font-size {
  font-size: 10px;
  transform: scale(0.8);
  transform-origin: left;
}

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