A Question About Body Sensor Block in Simscape

Based on Stewart platform model provided by matlab as example (it can be runned using the command mech_stewart_vis) in Simscape environment, I am trying to design a control system. I modified the output options of the Body Sensor block to output the rotation matrix(3X3 matrix) of the upper platform. However, the output is a vector of nine numbers. I don’t know which element in the rotation matrix corresponds to the element in the vector.

Thank you in advance for the help!