Dataset before being written to:
 [ 99 99 99 99 99 99 99 ]
 [ 99 99 99 99 99 99 99 ]
 [ 99 99 99 99 99 99 99 ]
 [ 99 99 99 99 99 99 99 ]

Dataset after being written to:
 [ 0 -1 -2 -3 -4 -5 -6 ]
 [ 0 0 0 0 0 0 0 ]
 [ 0 1 2 3 4 5 6 ]
 [ 0 2 4 6 8 10 12 ]

Dataset after extension:
 [ 0 -1 -2 -3 -4 -5 -6 99 99 99 ]
 [ 0 0 0 0 0 0 0 99 99 99 ]
 [ 0 1 2 3 4 5 6 99 99 99 ]
 [ 0 2 4 6 8 10 12 99 99 99 ]
 [ 99 99 99 99 99 99 99 99 99 99 ]
 [ 99 99 99 99 99 99 99 99 99 99 ]