Dan Ebberts answered my question on creative cow. 
"Colors need to be normalized to be between zero and one. So this should work to get 141:

myComp.property("Effects").property("Levels").property("Input White").setValue(141/255);"

I'm trying to add a levels effect to a composition and set the value for "Input Black" and "Input White" However, when I run the script in After effects I see values thousand above what I put in.  Here is my code: myComp.property("Effects").property("Levels")....