Have Float Social "float" a fixed distance from top

I’ve been playing around with Float Social and really enjoy the ability to customise the content (thanks for the tip AECNU).

However – as the user scrolls down the screen the box floats up to the top – and then continues downwards in tandem with scrolling action.

Is there an easy way to make it float in a slightly more central position (i.e. limit it to being no closer than 300px from top of screen) and *then* scroll down?

Edit: Just to clarify – I am aware of the ability to set the initial float position – but wanted to check whether there was a way to maintain it (i.e. arrest the float up to the top of the screen)