KenWood, You are correct so if you are flying Real world weather and that is what you want then you would fly real world weather and leave this alone.
But for those of us that fly to get different screenshots or just want to change the weather while we are flying you can change this slider setting
and open the FSX menu and click the weather tab and change the weather to any of the selections available.
chik, If you want very little cloud coverage just choose the weather theme in FSX to cold fronts or fair skies and set this slider all the way to the left,
this will give you just a few scattered clouds.
You have to use both of these Density slider and the FSX weather themes to adjust the weather to exactly what you want it to be.
just experiment with these some and you will figure out what works for you or not.
My System -
Dell Inspiron 580 Tower | FSX Deluxe Edition - Acceleration/SP2 | W-7/64 | Intel Quadcore i5 - 760 @ 2.93Ghz | 16GB@1600Mhz Corsair Vengeance Ram | EVGA SuperNOVA NEX750G Power Supply | EVGA GTX 660Ti FTW + LE 3GB GPU | Creative Soundblaster Z |
5TB Total Storage - 2TB + 1TB Internal High Performance 64MB Cache WD Caviar Black HDD's + 2 - 1TB WD External HDD's | 32" Samsung UN32F5500 LED HD Monitor | Klipsch Pro Media 2.1 Speakers