How to extract or capture the value from stdout_lines of an Ansible playbook?

I am looking for help to extract or capture the free MB value from the stdout_lines of an Ansible playbook execution and use that value as a criteria to proceed further in the playbook.

My task output is :

ok: [Host1] => {
    "changed": false,
    "invocation": {
        "module_args": {
            "commands": [
                "show file systems | inc flash:"
            ],
            "interval": 1,
            "match": "all",
            "retries": 10,
            "wait_for": null
        }
    },
    "stdout": [
        "*     1707192   (1.6 GB)        603744 (589.6 MB)      flash     rw  flash:"
    ],
    "stdout_lines": [
        [
            "*     1707192   (1.6 GB)        603744 (589.6 MB)      flash     rw  flash:"
        ]
    ]
}

I tried to use

- set_fact:
    my_var: "{{ disk_space.stdout_lines | regex_findall('\\b([0-9]{1,4}\\.\\d+)\\s+MB.*flash:$') }}"

But I always get an empty output:

ok: [Host1] => {
    "ansible_facts": {
        "my_var": []
    },
    "changed": false
}

I would like to capture 589.6 value from the output and assign it to variable to be used in my further play.

An other possible approach is shown in the following minimal example playbook

---
- name: Cisco 'show file systems'
  hosts: localhost
  become: false
  gather_facts: false

  vars:

    disk_space:
      stdout: "*     1707192   (1.6 GB)        603744 (589.6 MB)      flash     rw  flash:"
      stdout_lines:
        - "*     1707192   (1.6 GB)        603744 (589.6 MB)      flash     rw  flash:"

  tasks:

  - name: Show stdout with data cleansing
    debug:
      msg: "{{ disk_space.stdout | regex_replace('  *', ' ') }}"

  - name: Show value of 4th column in KB
    debug:
      msg: "{{ ( disk_space.stdout | regex_replace('  *', ' ') | split(' ') )[4] }} KB"

  - name: Show value of 4th column in MB
    debug:
      msg: "{{ ( disk_space.stdout | regex_replace('  *', ' ') | split(' ') )[4] | int / 1024 }} MB"

resulting into an output of

TASK [Show stdout with data cleansing] **********************
ok: [localhost] =>
  msg: '* 1707192 (1.6 GB) 603744 (589.6 MB) flash rw flash:'

TASK [Show value of 4th column in KB] ***********************
ok: [localhost] =>
  msg: 603744 KB

TASK [Show value of 4th column in MB] ***********************
ok: [localhost] =>
  msg: 589.59375 MB

Or even

  - name: Show value of 5th column after cleansing
    debug:
      msg: "{{ ( result.stdout | regex_replace('  *', ' ') | replace('(', '') | replace(')', '') | split(' ') )[5] }}"

with result of

TASK [Show value of 5th column] ****************************
ok: [localhost] =>
  msg: '589.6'