Node Red - Change payload

[
    {
        "id": "2538d9a0f9ca1275",
        "type": "tab",
        "label": "Change Payload",
        "disabled": false,
        "info": ""
    },
    {
        "id": "d72dc4ce.89b368",
        "type": "inject",
        "z": "2538d9a0f9ca1275",
        "name": "",
        "props": [
            {
                "p": "payload"
            },
            {
                "p": "topic",
                "vt": "str"
            }
        ],
        "repeat": "",
        "crontab": "",
        "once": false,
        "onceDelay": "",
        "topic": "",
        "payload": "a",
        "payloadType": "str",
        "x": 90,
        "y": 60,
        "wires": [
            [
                "5c77eb01735304a3"
            ]
        ]
    },
    {
        "id": "78075f19.e0174",
        "type": "change",
        "z": "2538d9a0f9ca1275",
        "name": "",
        "rules": [
            {
                "t": "change",
                "p": "payload",
                "pt": "msg",
                "from": "2",
                "fromt": "num",
                "to": "done",
                "tot": "str"
            }
        ],
        "action": "",
        "property": "",
        "from": "",
        "to": "",
        "reg": false,
        "x": 340,
        "y": 80,
        "wires": [
            [
                "78dc7c25.b90d54"
            ]
        ]
    },
    {
        "id": "78dc7c25.b90d54",
        "type": "debug",
        "z": "2538d9a0f9ca1275",
        "name": "",
        "active": true,
        "tosidebar": true,
        "console": false,
        "complete": "false",
        "statusVal": "",
        "statusType": "auto",
        "x": 550,
        "y": 80,
        "wires": []
    },
    {
        "id": "5c77eb01735304a3",
        "type": "random",
        "z": "2538d9a0f9ca1275",
        "name": "",
        "low": 1,
        "high": "5",
        "inte": "true",
        "property": "payload",
        "x": 140,
        "y": 200,
        "wires": [
            [
                "78075f19.e0174"
            ]
        ]
    }
]