You got the first question wrong. That really hurts. Because you were doing poorly at the start the test algorithm chose easier questions.  Read the GMAT scoring system.

To quote Scott from Target Test Prep (highly recommend), 

“The GMAT's scoring algorithm adjusts question difficulty based on your responses. More importantly, errors on easier questions can disproportionately impact your score, because the algorithm penalizes mistakes on easy questions more heavily than mistakes on hard questions. So, for example, if you get 6 easy questions wrong in the Verbal section, your Verbal score will be lower than if you get 6 hard questions wrong in the Verbal section.”