Why in the example after the execution of the convolution the output matrix did not mesh?

[nitr...@gmail.com]

Why in the example after the execution of the convolution the output matrix did not mesh?
The edges in the matrix should disappear
(it should not be 24x24, it should become 22x22 as it is here http://cs231n.github.io/convolutional-networks/)?

You can tell an example of convolution operations used in ConvNetJS?