This is an example of a SOA graph. The y-axis is the drain-source current, the x-axis is the drain-source voltage, and the dashed areas represent the amount of time the MOSFET can tolerate the power. Worst case conditions would be in the event of a short circuit where the entire load is across the MOSFET. First select the max voltage the system is operating under and draw a line up from the x-axis. Then select the current limit and draw a line from the y-axis and look at the intersection (8 or 9 ms in this example).