As soon as you receive your visa, check to make sure all your personal information printed on the visa is correct. If any of the information on your visa does not match the information in your passport or is otherwise incorrect, please contact the issuing authority (i.e. the U.S. Embassy) immediately.
The expiration date of your visa is the last day you may use the visa to enter the U.S. It does not indicate how long you may stay in the U.S. Your stay is determined by the Department of Homeland Security at your port of entry. As long as you comply with the Department of Homeland Security decision on the conditions of your stay, you should have no problem.
Further information about interpreting your visa can be found at the Department of State’s Consular Affairs website.