Explain a little more about nv_perf_level

We think this was a little confusing, so explain some more.

example/gamemode.ini

@@ -53,7 +53,9 @@ inhibit_screensaver=1
 ; See NV_CTRL_GPU_POWER_MIZER_MODE and friends in https://github.com/NVIDIA/nvidia-settings/blob/master/src/libXNVCtrl/NVCtrl.h
 ;nv_powermizer_mode=1
 
-; This corresponds to the performance level to edit in nvidia-xconfig (usually the highest level - on older cards 1, newer cards can be 4 or higher)
+; This corresponds to the performance level to edit in nvidia-xconfig
+; Set this to the highest level shown in the nvidia settings power mizer settings
+; Or from the command line check the highest perf value listed by "nvidia-settings -q [gpu:0]/GPUPerfModes"
 ;nv_perf_level=1
 ; (these two are Mhz offsets from the baseline, ie. 0 applies no change)
 ;nv_core_clock_mhz_offset=0