This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
Percentage is not shown on the certificate. Certified means certified. But someone scores good, he/she can mention in resume. It may give some impression.
One have chance of retake if fails, after passing no retake is given. It is not like that if you scored less but passed but want to score better in next attept. Retake is given (as per the current offer) if someone fails in first attempt.
First attempt scoring is not so bad but you can't be confident to go with exam in such an case. You can improve yourself by finding the reason why did you chose the incorrect options.