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Export Image: Different Title and Labels sizes

I would like to export a chart to a static image and keep the same title and labels size.
When I try to do this I got this different size results:

a) The chart image in my browser (Chorme)

b) The exported image (PNG):

Here is my config object:

const config = {
        showLink: false,
        editable: false,
        displayModeBar: true,
        displaylogo: false,
        modeBarButtonsToRemove: ['sendDataToCloud'],
        responsive: true,
        toImageButtonOptions: {
            format: 'png', // one of png, svg, jpeg, webp
            filename: 'plot',
            height: 2500,
            width: 2500,
            scale: 1 // Multiply title/legend/axis/canvas sizes by this factor

Please, could you help me?

Inside the toImageButtonOptions:

height: document.getElementById("myDiv").offsetHeight,
width: document.getElementById("myDiv").offsetWidth,