To subtract score would I do
%client.score - 5;
%client.score - 5; would just be like saying to someone "What is your age minus five"? It wouldn't actually make your age that value.
%client.score = %client.score - 5; would work because it would be like saying:
"Your age is now what your age is minus 5"
= stands for assignment, so it assigns what the expression on the right evaluates to to the left variable.
Edit: I just realized my example of "Your age is now" works well, because you couldn't do:
"Your age is now minus 5", that doesn't make sense and it would make you -5 years old. (%client.score = -5;)
You can do %client.score -= 5; because that is a built in feature in a lot of programming languages that basically shortens your statements.
%client.score += 5; or -= 5; or *= 5 or /= 5.
(idk if torquescript does modulus)