Hey Paul thanks for your response.
Yes I should have changed or deleted the comments, and yea there are many things I don't understand yet haha...
I did find a solution though if anyone else is looking for help here too:
my InputBufferSize was too small so in MatLab I put this code in:
s = serial('/dev/tty.usbmodem1421'); % define the 's' as the Arduino port
set(s, 'InputBufferSize', 1024);
the default is 512 and I was surpassing that if I created numbers too large in my grid (probably could have been fixed by not using an array but it works haha).