Horizontal stack is not using full width

I am not sure why the width is being constrained but it just isnt filling the screen as I assumed it would.

type: horizontal-stack
cards:
  - type: light
    entity: light.360178242462ab2e6253
  - type: light
    entity: light.deck
  - type: light
    entity: light.kitchen_ceiling
  - type: light
    entity: light.holiday_lights
  - type: light
    entity: light.chandelier
  - type: light
    entity: light.kitchen_4
  - type: light
    entity: light.living_room_lights

I think I figured this out. set panel to true in the configuration.

Yes, the best way is to use panel mode as you figured out, you can add several horizontal stacks into a ‘top-level’ vertical stack, e.g. if you would like to have several graphs spanning over the entire screen underneath each other.