diff --git a/README.md b/README.md
index ceb6eb2..9d59708 100644
--- a/README.md
+++ b/README.md
@@ -99,7 +99,6 @@ conf.probe.types=HttpAccessLog, HttpErrorLog
 conf.probe.httpaccesslog.file=/var/log/apache2/foo.bar.org-access.log*
 conf.probe.httperrorlog.file=/var/log/apache2/foo.bar.org-error.log*
 conf.probe.target=/srv/statoolinfos/well-known/statoolinfos/foo.bar.org.metrics
-
 ```
 
 Generate the metric file for the first time:
@@ -113,3 +112,5 @@ Create a cron file to update the metric file everyday:
 ```
 1 * * * * root /srv/statoolinfos/bin/probe -previousday /srv/statoolinfos/conf/foo.bar.org.conf
 ```
+
+Warning: in previous day mode, the metrics generated are overwrited for the last month, the last week and the last day. So, six weeks in logs are required.