scoring in a multiple choice quiz

Hello,

Sorry if this is the wrong palce to ask.  We have set up a multiple choice quiz.  The correct answer is selecting 4 options out of 6.  However, if they choose 2 correct options, and 2 incorrect options - this seems to negate itself, and equal zero.  We'd like it to equal 2 correct answers (out of 4).. How do I update that?  I can see you can turn off the "+1" or "-1" section on the answers, but then at the feedback/check answer stage and overall score it still seems to negate out a positive answer with a negative one.

Does anyone have any insight?! surely there's a way to override/change that..

Thanks so much.