Added info about growing counters

Author: nastena1606

Diff for: docs/backups-pitr.md

@@ -61,4 +61,6 @@ The available metrics are:
 * `pxc_binlog_collector_last_upload_timestamp` - Records the timestamp of the last successful binlog upload to the storage
 * `pxc_binlog_collector_uploaded_total` - The total number of successfully uploaded binlogs
 
-You can connect to this Pod using the `<pitr-pod-service>:8080/metrics` endpoint to gather these metrics and further analyze them.
+You can connect to this Pod using the `<pitr-pod-service>:8080/metrics` endpoint to gather these metrics and further analyze them.
+
+Note that the statistics data is not kept when the point-in-time recovery Pod restarts. This means that the counters like `pxc_binlog_collector_success_total` are reset.