You can try something like that:

\scoring{b=0,m=-2,d=1,p=-0.5}

• b=0 to score zero points when properly ticked or not
• m=-2 to score -2 points when an correct answer is not ticked or a wrong anser is ticked

Then the score will be 0 when all is OK or ≤-2 when something is wrong.

Then d=1 adds 1 to the total score, so that the score is now 1 when all is correct, or ≤-1 when something is wrong.

Then p=-0.5 sets a ceiling value to -0.5, leading to the required result.

Alternatively, you can use a formula:

\scoring{formula=(N==NBC+NM-NMC ? 1 : -0.5)}

Here, N is the number of answers, NB number of correct answers, NBC number of correct ticked answers, NM number of wrong answers, NMC number of wrong and ticked answers.

Note that with a recent version of AMC you can test your scoring strategy with this window:

Thanks @Alexix, for a quick response! The strategy given in your reply works flawlessly! Exactly the way I wanted it to work...

Regarding the "Test Scoring", it took me some time to understand `how to use', but it was smooth once it clicked! A frank feedback: the modus operandi is a bit less intuitive!

Thanks once again!
-- VInay