<h1 class="cp_h1title">見出しテキスト1</h1>
<h1 class="cp_h1title">見出しテキスト2</h1>

.cp_h1title {
  counter-increment: titleNum;
  position: relative;
  border-bottom: 1px solid #FFCC80;
  padding: 0 0 0 2em;
}
.cp_h1title::before {
  position: absolute;
  content: counter(titleNum);
  font-size: 90%;
  top: calc(50% - 0.75em);
  left: 0;
  color: #fff;
  background-color: #FF9800;
  width: 1.5em;
  height: 1.5em;
  text-align: center;
  border-radius: 50%;
}