How do &#39;rules developed entirely by judicial decisions&#39; differ from &#39;new rules made by judges when they interpret statutes&#39;?
<p><sub>Source: p 5, <a href="https://www.amazon.co.uk/gp/product/0414041801/ref=pd_sbs_14_t_1?ie=UTF8&amp;psc=1&amp;refRID=8AWSERSMKG5WTHNPGVKS" rel="nofollow"><em>How to Study Law</em></a> (2010 6 ed) by A Bradney, F Cownie, J Masson, A Neal &amp; D Newell.</sub></p>

<blockquote>
  <p><strong>Precedents</strong><br>
  Not all legal rules are laid down in an Act Of Parliament or some other piece of legislation. A 
  number of legal rules are found in the statements of judges made in the course of deciding 
  cases brought before them. Rules that come from judicial decisions, rather than from legislation, make what is called the common law. A common law rule has as much force as a rule 
  derived from statute. Many important areas of English law, such as contract, tort, criminal law, 
  land law and constitutional law have their origins in common law. An explanation of the different divisions Of law is to be found in Chapter 2. Some of the earliest common law rules still 
  survive, though many have been supplemented or supplanted by statute. Common law rules are still being made today, though, as a source of new legal rules, common law is much less important than statute.<br>
     Strictly speaking, the term common law is confined to <strong>[1.]</strong> rules that have been developed 
  entirely by judicial decisions <strong>[End of 1.]</strong>.<br>
  It excludes <strong>[2.]</strong> <code>new rules made by judges when they interpret statutes</code> <strong>[End of 2.]</strong>. Most decisions made by judges now involve, at least in part, interpreting statutes.<br>
  <strong>[3.]</strong>  The 
  term <em>case law</em> covers both kinds of decisions <strong>[End of 3.]</strong>. </p>
</blockquote>

<p>3 states that case law = 1 + 2, but I cannot discern the differences between 1 and 2.<br>
I use the Set Theory symbol ⊆ to mean 'is a (proper) subset of'.</p>

<ol start="4">
<li>How exactly does 2 differ from 1? Why is not 2 ⊆ 1, because<br>
judicial decisions (per 1) ⊆  statutory interpretation or legislation (per 2)?</li>
</ol>

<p>I understand numerical distribution of the sources of law possibly to vary for different cases: but 2 appears not to mean this. </p>

judging