How to slice two layers of columns?

Hello,
 
I need to cut the header of the columns of the classic mode table into two layers. But after trying so many times, it seems like can only be divided from rows, but my data format is not supported. Or maybe there's something wrong with my approach.
 
The picture is the result I want. Here's my data:
 

[
        {
          "_id" : "测试制作中心2021-04",
          "region" : "委外",
          "total" : 40000,
          "max" : 20000,
          "min" : 0,
          "month" : "2021-04",
          "work_center" : "测试制作中心"
        },
        {
          "_id" : "西安制作中心2021-03",
          "region" : "委外",
          "total" : 14000,
          "max" : 12000,
          "min" : 0,
          "month" : "2021-03",
          "work_center" : "西安制作中心"
        },
        {
          "_id" : "西安制作中心2021-04",
          "region" : "委外",
          "total" : 26000,
          "max" : 26000,
          "min" : 26000,
          "month" : "2021-04",
          "work_center" : "西安制作中心"
        }
]

 
Thanks!