diff --git a/docs/icub_robot_calibration/icub3-stator-rotor-autocalibration.md b/docs/icub_robot_calibration/icub3-stator-rotor-autocalibration.md
index 3f8cf84a1..ec5c66a6d 100644
--- a/docs/icub_robot_calibration/icub3-stator-rotor-autocalibration.md
+++ b/docs/icub_robot_calibration/icub3-stator-rotor-autocalibration.md
@@ -41,6 +41,8 @@ Once `yarprobotinterface` is running, check the log messages and look for a `DEB
 
 Looking at par64, the rightmost 4 digits are the offset: `0x0079` = `121` degrees; this is the value to save in the file (see next steps). 
 
+The first `DEBUG` messages have the rightmost 4 digits equal to the default value `0xffff` until the offset is not found. 
+
 !!!warning
     The 8 leftmost digits (in the example `0xffcc0042`) must be not `0`!<br>
     Otherwise the calibration is failed/not completed.