The Signal System screen displays a field called Rating. Rating appears after a new signal system is saved. Rating is an overall rating and is based on the condition of equipment at the signal system. Having just created the signal system, there will be no equipment and therefore no rating (i.e. Missing Equipment).
The Rating is automatically recalculated each time Main Equipment changes. The Main Equipment, the condition of the Main Equipment and the condition of Supports will impact the rating calculation.
For more information on how the Rating is calculated see Rating Calculation.