It's basically Construct 2's proprietary format that's probably not intended for manual edition.
The "data" field is a nested array (1-dimensional table of items delimited by square brackets []). In the case of Hardware Tycoon, the first level (so the second pair of square brackets) is a column, with every field being its own one-element array.
So for example:
"data":[[[1],[2]], [[3],[4]]]
would be a 2D table that looks like this:
| 1 | 3 |
| 2 | 4 |