These are the Variables the game itself uses. Don't use these Variables in your PSA, unless it's being specifically used with what the game uses it for.
Look at this thread to know which Variable ranges both Brawl and PM use.
http://forums.kc-mm.com/index.php?topic=74266.0To set/clear Variables, it depends on the type of Variable (Basic, Float, and Bit). With Basics and Floats, you can't really use commands to clear them, but you can use the associated commands to reset the Variables in question. You won't have issues setting and clearing Bits though.
Float: Float Variable Set (sets a Float Variable), Float Variable Add (adds to an associated Float Variable), Float Variable Subtract (subtracts from an associated Float Variable), Float Variable Multiply (multiplies an associated Float Variable), and Float Variable Divide (divides an associated Float Variable).
Basic: Basic Variable Set (sets a Basic Variable), Basic Variable Add (adds to an associated Basic Variable), and Basic Variable Subtract (subtracts from an associated Basic Variable).
Bit: Bit Variable Set (sets a Bit Variable) and Bit Variable Clear (clears a Bit Variable).
If a Variable in general is giving you trouble with your custom coding, either remove any trace of the Variable, or use a different Variable.