Fieldset "grid", show separate entries in collection columns

Hope that title makes sense!

My collection has a grid fieldset:

the_field:
  type: grid
  fields:
    first_field:
      type: text
      mode: number
    second_field
      type: text

In CP, in the collection overview, I would like to show these entries in columns.

In folder.yaml I've added:

title: My collection
columns:
  - title
  - the_field

But that returns an [object Object].

When I change it to the_field.first_field I get an error. Same goes for the_field.0.

What I'd really like is to be able to have separate columns for first_field and second_field, but I can absolutely work with showing both fields in one the_field column.

Hope anyone can point me in the right direction ;-)