Extjs Chart numeric y-axis as integer

JavaScript

offset = -9;

var store1 = Ext.create('Ext.data.Store', {
    fields: ['name', {name: 'people', type: 'integer' }],
    data:[
        {"name":"jan",  "people":13+offset},
        {"name":"feb",  "people":12+offset},
        {"name":"mar",  "people":12+offset},
        {"name":"apr",  "people":13+offset},
        {"name":"may",  "people":12+offset},
        {"name":"june", "people":13+offset}
    ]
});

var chart = Ext.create('Ext.chart.Chart', {
    renderTo: Ext.getBody(),
    width: '80%',
    height: '80%',
    store: store1,
    axes: [{
        type: 'Numeric',
        position: 'left',
        fields: ['people'],
        majorTickSteps: 1,
        minimum: 0,
        maximum: 5,
        label: {
    renderer: function (v) {
        return v.toFixed(0); 
    }
}
    }, {
        type: 'Category',
        position: 'bottom',
        fields: ['name'],
    }],
    series: [{
        type: 'line',
        axis: 'left',
        xField: 'name',
        yField: 'people',
    }]
});