One number belongs to the piping and the tank. The other belongs to the pump. Cavitation starts the moment the system's number stops covering the pump's.
NPSH-A (Net Positive Suction Head Available) is a property of the installation — the tank elevation, the atmospheric or vessel pressure, the liquid's vapor pressure at its pumping temperature, and the friction loss in the suction piping between the source and the pump flange. NPSH-R (Net Positive Suction Head Required)is a property of the pump itself — a curve the manufacturer measures on a test stand and publishes alongside the head-vs-flow curve, describing how much suction head that specific impeller design needs at each flow rate to keep the local pressure at the impeller eye above the liquid's vapor pressure. Neither number means anything about cavitation risk on its own. What matters is the comparison between them, at the flow rate you actually run.