This quiz doesn't let you go back to correct your answers if you got one wrong. Which ever one you click it goes to the next question. But, It might be the font having issues |'D It was messing with me before too. The font reacts differently with different computers It will make the second digit disappear for some reason sometimes. It's a bug I have tried to fix over and over again. I'm sorry for that. ;^; So I would think it might just be the font freaking out for the most part.
If you know you got all correct, that's all that matters! 10 out of 10! ;v; Congrats!! x33