You dont get array as a result. You get stdClass which is an object.
You have to access its property. And that property is an array that contains an element that is a json encoded string, so you have to decode it first and then access array key that you are interested in.
Also you didnt specify which product data you are interested in (from row or rows property? Can there be more rows?).
https://www.php.net/manual/en/language.types.object.php
https://www.php.net/manual/en/function.json-decode.php
<?php
$data = new stdClass();
$data->num_rows = 1;
$data->row = [
'setting' => '{"name":"featured","product_name":"","product":["176","143","60"],"limit":"10","width":"200","height":"200","status":"1"}',
];
$data->rows = [
0 => [
'setting' => '{"name":"featured","product_name":"","product":["176","143","60"],"limit":"10","width":"200","height":"200","status":"1"}'
]
];
// get product array from row
var_dump(json_decode($data->row['setting'])->product);
// get product array from first row of rows
var_dump(json_decode($data->rows[0]['setting'])->product);
// get product array from all rows
array_map(function(array $row) {
var_dump(json_decode($row['setting'])->product);
}, $data->rows);
All 3 dumps result in:
array(3) {
[0]=>
string(3) "176"
[1]=>
string(3) "143"
[2]=>
string(2) "60"
}