Fuji Electric PXF9APC2-MBVA1 1/4 DIN Temp Controller, 50ms

What does the 50 ms sampling speed mean on a temperature loop?

It means the controller reads the input, runs the PID algorithm, and updates the output every 50 milliseconds — fast enough to track a rapid thermal transient on a small furnace or a plastic-injection nozzle where a standard 250 ms controller would lag and overshoot.