maxWidth option has a default of 400 and the code appends 'px' unit to it when it applies the style to the Sezzle widget.
https://github.com/sezzle/static-widgets/blob/production/src/awesomeSezzle.js#L153
This is too restrictive to hardcode the 'px' unit in the widget code. Ideally, it should leave the unit to the consumer of this widget to whatever they want to use, thus also allowing them to also use keyword values such as 'none', 'max-content', etc.