Clarify font-size: math procedure step (#298)

Author: eerii

spec.html

@@ -5153,7 +5153,7 @@ <h3>The <code>math-depth</code> property</h3>
               <li>Otherwise B &gt; A and set <code>InvertScaleFactor</code> to false.</li>
             </ul>
           </li>
-          <li>Let E be B - A &gt; 0.</li>
+          <li>Let E be B - A, which is positive.</li>
           <li>If the inherited <a>first available font</a> has an OpenType MATH table:
             <ul>
               <li>If A ≤ 0 and B ≥ 2 then multiply S by <a>scriptScriptPercentScaleDown</a> and