These days, a question like that is easy to answer: type it in to Google, click on the Wikipeadia entry, and read the answer: 2306 +/- 20 km. The  +/- (to be read "plus or minus") is important here: every measurement has limitations and an often critical  part of science is correctly quantifying those limit. The correct interpretation of 2306 +/- 20 km is that 2306 km is the most likely value,