Clarify elementCompleteness and negative weights

Author: kkraune

en/reference/rank-features.html

@@ -705,7 +705,9 @@ <h3 id="features-for-indexed-multivalue-string-fields">Features for indexed mult
 
 <tr><td>elementCompleteness(<em>name</em>).elementWeight</td>
   <td>0</td>
-  <td><p id="elementCompleteness(name).elementWeight">The weight of the best matching element.</p></td></tr>
+  <td><p id="elementCompleteness(name).elementWeight">
+    The weight of the best matching element, starting from the default - i.e., negative weights will return 0.
+  </p></td></tr>
 
 <tr><td>elementSimilarity(<em>name</em>)</td>
   <td>0</td>