What does R stand for in G02G03 CNC milling machine, and the difference between it and I.J.K.

G02/03 is followed by R. R refers to the size of the circular arc interpolated by G02/03, which is generally less than 180 degrees. I, j, k are the vector values of the starting point relative to the center of the circle, I is the X-axis direction, J is the Y-axis direction, and K is the Z-axis direction (I= the X-coordinate of the center minus the X-coordinate of the starting point, J= the Y-coordinate of the center minus the Y-coordinate of the starting point, and K= the center z).