What does "Normalized to Si 10 to the power 6" mean? I'm writing a space game that I want to give a more "realistic" feel. When looking for a reference as to distribute elements in planets (for mining, etc) Instead of finding the more usual percentage tables, it seems that all elements are presented in a "normalized to Si 10 to the power 6", and furthermore, it seems that the data is presented as number of atoms, instead of actual mass. I've been searching this for days, and even the "parts per million/billion/trillion" tables sometimes just jump for percentages, where is is again no clear if what is being referred to are masses or number of atoms. Could someone clarify this, or better, point me to a mass percentage table of elements in a solar system/galaxy for reference? Thanks in advance.
The table you referenced is normalized so that the abundance of Silicon (Si) is exactly $10^6$, and all the other numbers are related to that.

"Abundance" in this table refers to the number of atoms.

Please note that this table is for the entire Solar System, taking into account the huge amounts of Hydrogen and Helium in the Sun. It will not be appropriate for creating Earth-like planets.