Need help with Card Mod

Configuration Frontend
1

Hi All

I am in the process of Setting up my Dashboard. I have this light card (custom mushroom card) that i would like to increase the size of the font. I am unable to do it and get error message.

Can you point me out where i am making a mistake and help me fix it please ?

type: custom:mushroom-light-card
entity: light.kitchen_lights
show_entity_picture: false
vertical: true
hide_state: false
state_content:
  - brightness
  - state
tap_action:
  action: toggle
icon_tap_action:
  action: more-info
layout_options:
  grid_columns: 2
  grid_rows: 2
name: Kitchen
card-mod:
  style: |
  ha-card {
    size: 10px;
  }
2

This is how my card looks now and I would like to increase the font size ? but for some reason my YAML code above doesn’t work. i am not sure where i am going wrong

image