If I know how many questions I attempted/got wrong on GRE Math Subject test, can I estimate my score? I gave my Mathematics GRE Subject test yesterday ( 170 minutes). I attempted 42 out of 66 questions and feel I could do more if I had some more time. I lost time solving some questions. 

Of the questions I attempted, I took my time and at most only 3-4 might have been attempted wrong. 

Do I have chances of receiving a really low score? How can I estimate my score?
The official practice book for the Math Subject Exam describes how to score an exam.

According to this practice book, a typical scaled score in 2008-2009 for someone with a raw score of 41 (42 correct answer, 4 incorrect answers = 41 raw score) might be around 730, or 72nd percentile. 

You can calculate the score for other possible scenarios following the procedure described in the practice book.

As for whether this is considered a "really low score," please see What is an acceptable math GRE subject score.