It means that the pitch mode has failed and that the autopilot is now functioning at a degraded mode. The amber line notifies you of a persistent problem that needs attention. It points to the fact that the autopilot cannot function to its best capabilities. It is important to read and understand the EICAS messages as they point to valuable situations that can have a major impact on the operating system.
When you know how to interpret the signals, you can evaluate the system, troubleshoot the problem or figure out the best way out of the problem. However, if you are unable to understand the signals, you will not be able to take the necessary actions.