Final answer:
The documentation system used by the nurse, which records only the abnormal findings, is known as charting by exception.
Step-by-step explanation:
The documentation and informatics system being described is known as charting by exception. This method involves noting only those findings that deviate from predefined norms or standards. In the given case, the nurse records only the abnormal findings—a casted left lower extremity due to a heel fracture and pain in the left foot—while all other physical exam and review of system findings are within normal limits, and therefore not explicitly documented. This approach streamlines the documentation process and highlights only the information that requires attention.