How to use template to access these entity attributes? This is from the Office 365 calendar integration

Configuration
1

How do I access the items under “data:” below using a template? I can get the top level items using {{ state_attr("calendar.my_calendar", 'message') }} or {{ state_attr("calendar.my_calendar", 'all_day') }} but not sure how to go deeper under “data:”

message: xxxxxxxxxxxx
all_day: true
start_time: '2023-08-01 00:00:00'
end_time: '2023-08-09 00:00:00'
location: ''
description: ''
offset_reached: false
data:
  - summary: xxxxxxxxxxxx
    start: '2023-08-01'
    end: '2023-08-09'
    all_day: true
    description: ''
    location: ''
    categories: []
    sensitivity: Normal
    show_as: Busy
    attendees: []
    uid: >-
      -xxxxxxxxxxxx-Ew5kCG4AtrJCWBkAAAAgENAAAA8u0cL-Ew5kCG4AtrJCWBkAAHJsuQagAAAA==
  - summary: xxxxxxxxxxxx
    start: '2023-08-03'
    end: '2023-08-09'
    all_day: true
    description: ''
    location: ''
    categories: []
    sensitivity: Normal
    show_as: Busy
    attendees: []
    uid: >-
      xxxxxxxxxxxx-yYVgcA8u0cL-Ew5kCG4AtrJCWBkAAAAgENAAAA8u0cL-Ew5kCG4AtrJCWBkAAHGAtl0gAAAA==
  - summary: xxxxxxxxxxxx
    start: '2023-08-05T17:00:00+00:00'
    end: '2023-08-05T22:00:00+00:00'
    all_day: false
    description: ''
    location: Our House
    categories: []
    sensitivity: Normal
    show_as: Busy
    attendees: []
    uid: >-
      xxxxxxxxxxxx-yYVgcA8u0cL-Ew5kCG4AtrJCWBkAAAAgENAAAA8u0cL-Ew5kCG4AtrJCWBkAAHOdIZCwAAAA==
friendly_name: Calendar
2

This should give you the value of summary under the first block of the data attribute

{{ state_attr('calendar.my_calendar', 'data')[0].summary}}

Also be careful about mixing your quotation marks. They all need to be the within the template brackets