Relative Gain Array matrix calculations

Hello, I have a system with 13 inputs and 6 outputs. when I calculate the RGA for the whole system ( 13*6 matrix ), I get different results from when I calculate RGA for each process separately. the code :

matrix = [13*6]
matrixpi = pinv(matrix)
matrixtr = transpose(matrixpi)
RGA = matrix.*matrixtr

when I calculate the RGA for the whole system, in some cases, the numbers are very high( which is unusual. e.g. 5235589) but when I calculate the RGA for each process separately the numbers are more logical but in some cases result is different.

which method should I use for my calculations? the RGA for the whole system or separate RGAs?

Why the results are different?

thank you in advance