Linux 从 Ansible 中的 shell 命令输出中提取特定数据

I would like to create a playbook that extract the used space for /boot through the shell command df -B MB.
For this example, the playbook will show 358MB for the controller node.

I would like to know how to filter the server_info.stdout_lines in order to get the desired result.
I believe that we can do it with the regex_search filter.

 - hosts: all
      gather_facts: True
      become: True
      tasks:
        - name: show used space on /boot
          shell: "df -B MB"
          register: server_info

        - debug:
            msg: "{{ server_info.stdout_lines }}"

TASK [debug] *****************************************************************************************************************
ok: [control] => {
    "msg": [
        "Filesystem          1MB-blocks   Used Available Use% Mounted on",
        "devtmpfs                1458MB    0MB    1458MB   0% /dev",
        "tmpfs                   1488MB    1MB    1488MB   1% /dev/shm",
        "tmpfs                   1488MB   10MB    1478MB   1% /run",
        "tmpfs                   1488MB    0MB    1488MB   0% /sys/fs/cgroup",
        "/dev/mapper/cs-root    19267MB 6268MB   13000MB  33% /",
        "/dev/sda1               1064MB  358MB     706MB  34% /boot",
        "tmpfs                    298MB    1MB     298MB   1% /run/user/42",
        "tmpfs                    298MB    1MB     298MB   1% /run/user/1000"
    ]
}
ok: [ansible2] => {
    "msg": [
        "Filesystem          1MB-blocks   Used Available Use% Mounted on",
        "devtmpfs                1458MB    0MB    1458MB   0% /dev",
        "tmpfs                   1488MB    0MB    1488MB   0% /dev/shm",
        "tmpfs                   1488MB   10MB    1478MB   1% /run",
        "tmpfs                   1488MB    0MB    1488MB   0% /sys/fs/cgroup",
        "/dev/mapper/cs-root    19267MB 6264MB   13003MB  33% /",
        "/dev/sda1               1064MB  360MB     704MB  34% /boot",
        "tmpfs                    298MB    1MB     298MB   1% /run/user/42",
        "tmpfs                    298MB    1MB     298MB   1% /run/user/1000"
    ]
}