<!DOCTYPE html>
<style type="text/css">
  @counter-style a {
    system: extends decimal;
    suffix: ",";
  }
  @counter-style b {
    system: extends decimal;
    suffix: \3001;
  }
  ol {
    list-style-position: inside;
  }
  ol, section, p {
    padding: 0; margin: 0;
    line-height: 150%;
  }
  section {
    counter-reset: p -3;
  }
  p {
    counter-increment: p;
  }
  p::before {
    content: counter(p, a);
  }
</style>
<ol start="-2" style="list-style-type: a">
  <li>-2<li>-1<li>0<li>1<li>2
</ol>
<ol start="-2" style="list-style-type: b">
  <li>-2<li>-1<li>0<li>1<li>2
</ol>
<section>
  <p><p><p><p><p>
</section>