I seem to recall there being some tutorials about the probe light node by someone (Relik, I think? ) over at RDNA. He goes into a lot of detail on what the various paramteres of the probelight node do, and what they mean.

In a nutshell, each of the various settings marked 'value'  refers to a different direction the light can come from - the 'value' in question is the RGB value of light from that direction. What you need to do - and I recommend finding those tutorials to check which value you need to change it to - is to turn of the 'light' coming from the bottom, and find the setting which controls 'light' from the left. you don't actually need to rotate anything at all.

JonTheCelt