[modeller_usage] origin of blosum62.sim.mat and as1.sim.mat

Hello, I am curious about the origin of the blosum62.sim.mat and as1.sim.mat. When I look at the blosum62.sim.mat, I can't figure out the relationship between the numbers there, and the original blosum62 matrix. Initially, I thought that the Henikoff & Henikoff values were just scaled to between 0 and 1000, but that didn't seem to work. I can't find a reference for ALBASE3 mentioned in as1.sim.mat. Finally, if I wanted to use my own matrix, is it necessary for me to scale it to between 0 and 1000? Your help in understanding this is greatly appreciated, Josh