Document behavior of length
@@ -3,9 +3,10 @@ namespace=vespa.config.search.summary
## Set the length (in #characters) of the dynamically generated
## summaries. This is a hint to the module that generates the
-## dynamic summary. The result may be slightly longer or shorter
-## depending on the structure of the available document text and
-## the submitted query.
+## dynamic summary - the actual size will depend on the available text
+## and the query. You may find that you need to set this length
+## substantially longer than your actual desired average length -
+## setting this abut twice as long is often appropriate.
length int default=256
## The number of (possibly partial) set of keywords
