Induction motor - d-q model
u in Simulink indicates the input signal of the block, therefore the gain of that block is KS. I would expect KS to be the matrix you have in the equation, but we can't know for sure from the screenshot.

What you can guess is that, as an 3x1 array of van, vbn and vcn is given as an input to the block, and an 1x2 array with vqsS and vdsS is returned, the gain should be a 2x3 matrix.