{
    "tiers": {
        "$dynamic.list.next_index": {
            "total_exp_required": "$general.number",
            "trades": "$trade_table.general.trades",
            "groups": {
                "$dynamic.list.next_index": {
                    "trades": "$trade_table.general.trades",
                    "num_to_select": "$general.number"
                } 
            }
        }
    }
}