OK, some questions remain:
-- Is "n" (the number of reads) known in advance?
-- Your string has only 6 numbers, but you need seven.
-- Do you really need the first column to be 1,2,3,4,5,6,7?
-- Why a 5x5 array??
There are several ways to do this. If N is not known at the beginning, you need to append each new row to the existing array.
If N is known, you can initialize a 2D array at the final size. In this case you would use "replace array subset", keeping the array size constant. This is more efficient.
(You were using "Insert into array" which actually adds colums, thus growing the array and making the earlier preallocation of the 2D array pointless.)
I have attached a quick demo that shows suggested code for each v
ersion. Just run it and press stop after a while. I have also modified the string to produce 7 integers.
In your case you would need to get a new string from the device in each iteration. Modify as required. Good luck!