Use numeric value of nested json data in Extjs 4 chart

[skylinezpromise]

My json looks like this :

{
    "Week": [
        1224,
        {
            "Total_OUT3F": 12,
            "Sev_Logged": "3_major",
            "Total_OUT3A5": 3,
            "IN1": 36,
            "OUT3FA_5": 15,
            "Total_IN1": 36,
            "OUT3A_5": 3,
            "OUT3-Fix": 12
        },
        1225,
        {
            "Total_OUT3F": 24,
            "Sev_Logged": "3_major",
            "Total_OUT3A5": 12,
            "IN1": 21,
            "OUT3FA_5": 21,
            "Total_IN1": 57,
            "OUT3A_5": 9,
            "OUT3-Fix": 12
        },
        1226,
        {
            "Total_OUT3F": 49,
            "Sev_Logged": "4_minor",
            "Total_OUT3A5": 17,
            "IN1": 40,
            "OUT3FA_5": 30,
            "Total_IN1": 97,
            "OUT3A_5": 5,
            "OUT3-Fix": 25
        }]}

I'd like to get the "Week" values (1224,1225,1226) in the X axis of my chart. How can I do this please ?
This is my model :

Ext.define('Metrics.model.GraphData', {
    extend: 'Ext.data.Model',
    fields: ['Week', 'OUT3FA_5','OUT3A_5','IN1','OUT3-Fix','Total_IN1','Total_OUT3F','Total_OUT3A5']
});

In my Chart js file, I put

xField = 'Week'

but it doesn't take the numeric values.
Please any help would be appreciated.

[mitchellsimoens]

The week number needs to be within the object