I’ve done some reading but I’m still lost 
Where are you seeing that?
Anyway, gpu latency is a description of how long it is taking for your graphics card to rasterize (convert vector data to raster [pixel] data) and output it to your computer’s monitor. 
shadows, textures, geometry, all add up,
screencasting eats gpu time as well I think.
GPU latency is the amount of time your CPU wastes doing nothing while it waits for the GPU to catch up. A high latency means you are giving the GPU a lot more work than the CPU (relative to what they can handle). What this also means is you can add more CPU intensive tasks (physics, AI, etc.) without affecting framerate since the CPU is already waiting on the GPU. If you are having framerate issues with high GPU latency, then you’ll need to tone down your graphics effects. It is hard to tell which effects are slowing down your scene without knowing more about your scene. If your framerate is fine, then I wouldn’t worry.
Two things that usually cause this in my game are v-sinc and 2d filters.
You can turn off vsinc in the game engine render options panel. This will correct the problem 99% of the time.
2d filters sometimes cause this problem too when they have recursive loops. Unrolling the loops usually fixes the problem, so if you use a 2d filter try to find an unrolled version (one which has been written specifically to avoid this issue) or reduce the number of passes/samples. I think it’s something to do with recursion limits in the code so that once recursion depth goes over a certain limit it suddenly takes A LOT more processing time to run the filter.
That you shouldn’t throw your computer at the ceiling?
My gpu latency goes through the roof when I add a ragdoll from a makehuman model. It’s only about 2000 vertices total (visible mesh + collision boxes), does anyone know what could be causing this?