Why does my 2nd GPU always seem to have the higher Usage?

That's a little odd - isn't the GPU1/First GPU supposed to be doing majority of the work?

Games like The Witcher 3 right now show that my 2nd GPU is averaging around 98% usage but my 1st GPU is around 80 - sometimes 95%.

Oh and on my Afterburner Monitor - it shows each card is using 'max' 2160Mb of VRAM. - This is my first SLI setup - so does each GPU split the load evenly?

For instance, I've got two GTX 980s in SLI, 4GB a piece, but obviously not 8GB total. So since I've got 4GB available - do they each separate the VRAM in half?

Seems backasswards to me.. any ideas?