How to expand figure south to the complete south?

I do `plot(u); movegui(gcf, 'south');` but it takes only part of the south. I want that it takes the complete space at the top (south).

MATLAB: 2016b OS: Debian 8.5

[Geoff Hayes]

SL - you may need to clarify what the problem is. Perhaps attach a screen shot showing how far south the figure has moved.

[Walter Roberson]

Are you using multiple monitors?

Is the space left open possibly normally used for window decorations or toolbars?