Simrad AP28 Operator's Manual page 73

Confirm Rudder feedback calibration to starboard by
pressing the MENU key.
Manually turn the
helm/wheel to port
until the rudder stops
at port lock (H.O.).
Adjust the displayed angle the same way as for starboard
rudder.
Confirm Rudder feedback calibration to port by pressing
the MENU key.
Many boats have ±45° (90° H.O. - H.O.) rudder angle as
standard. So if you are not going to make any adjustment
to the displayed angle you should still highlight the
reading and confirm. This is necessary to prevent the
rudder from hitting the end stops.
Rudder zero may still be inaccurate and should be
adjusted under the next menu item.
MENU
MENU
Setup at installation | 73