diff --git a/doc/manual.xml b/doc/manual.xml
index d5e3755..cbc6a2c 100644
--- a/doc/manual.xml
+++ b/doc/manual.xml
@@ -219,7 +219,7 @@
              </entry><entry>off</entry></row>
 	    <row><entry><option>--thread-stack-size</option></entry><entry>Size of stack for each thread</entry><entry>32K</entry></row>
 	    <row><entry><option>--init-rng</option></entry><entry>Specifies if random numbers generator should be initialized from timer before the test start</entry><entry>off</entry></row>
-	    <row><entry><option>--report-interval</option></entry><entry>Periodically report intermediate statistics with a specified interval in seconds. 0 disables intermediate reports</entry><entry>0</entry></row>
+	    <row><entry><option>--report-interval</option></entry><entry>Periodically report intermediate statistics with a specified interval in seconds. Note that statistics produced by this option is per-interval rather than cumulative. 0 disables intermediate reports</entry><entry>0</entry></row>
 	    <row><entry><option>--test</option></entry><entry>Name of the test mode to run</entry><entry><emphasis>Required</emphasis></entry></row>
 	    <row><entry><option>--debug</option></entry><entry>Print more debug info</entry><entry>off</entry></row>
 	    <row><entry><option>--validate</option></entry><entry>Perform