Not sure what you want or are expecting because you forgot to tell us. Perhaps you want a 1-dimensional, 4-element vector. If so, here is how to do it.
xi = randi([10, 30], 4, 4)
0 -7 -16 2
If you want a 2-D matrix, then C=A-B works with no error in recent versions of MATLAB that do implicit expansion. But you also forgot to list your release when you posted. Here is another chance to read the posting guidelines and edit your post to improve it: