using form fields while binding signature , Signature is binding at the bottom of the document

While I am using the adobe api form fields while I am binding the form fields I am unable to bind at the particular x and y axis  point. By default signature is binding at the bottom of the form. 

I am using the below format :

{
    "fields": [
        {
            "locations": [
                {
                    "height":35,
                    "left": 160,
                    "pageNumber": 1,
                    "top": 84,
                    "width": 276
                }
            ],
            "readOnly":"true",
            "contentType": "SIGNATURE",
            "name": "Test For Binding The Data 1",
            "inputType": "SIGNATURE",
            "recipientIndex": 1,
            "alignment": "LEFT",
            "required": "true",
            "visible": "true",
            "tooltip": "Enter Signature Test",
            "assignee": "**************************************",
           "action":"SHOW"
        }
    ]
}.