This is an over-range condition that can be fixed by performing an Electronic calibration of the circuit board. Please see directions in the Operations Manual or follow this brief review of Electronic Calibration.
Hook up a Multi-Meter to the R+ and R- leads located at the top of the circuit board, switch the Multi-Meter to DC volts, push the Full Scale Push to Test button and read the DC voltage on the Multi-Meter.
While pushing the Full Scale Push to Test button, adjust the CAL screw on the circuit board until the Multi-Meter reads 9.95-10.00 VDC. The display on the Myron L Monitor or Monitor/Controller should now read Full Scale.

Source: Myron L FAQ