The "Abandon immediately whenever cannot pass" option refers to the Pass score percentage.
If you have entered a 50% Pass score, for instance, and the learner has already answered more than 50% of the answers wrong before going through all the questions, the system will automatically exit the test and show a message like this:
The percentage shown here indicates the maximum score the learner could reach if they answered correctly the questions left unanswered. Since this percentage is less than the indicated pass score, the test is automatically failed.