Operational risk is the primary risk of TSP processing and can drive reputation, strategic, compliance, credit, interest rate, liquidity and price risk for the serviced institutions; the quantity of operational risk at a TSP is the level of risk present and the quality of its management is how well risks are identified, measured, controlled and monitored, which is what the agencies rate.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.