the following is from this website:
http://www.dwra.net/settingrecords.htm
As in any sport, competitors seeking to establish land speed records must follow an established set of rules. World records in land speed competition are recognized by the Federation Internationale de l'Automobile (FIA) only if they meet rigid international standards. Those standards are enforced by each individual country's sanctioning body.
American auto racing is so diverse that it became necessary years ago to form a committee so that all the major sanctioning bodies would have representation. The result is the Automobile Competition Committee of the United States (ACCUS), and is comprised of members from United States Auto Club (USAC), National Association for Stock Car Auto Racing (NASCAR), Sports Car Club of America (SCCA), National Hot Rod Association (NHRA) and Professional Sports Car (PSC). Typically, USAC and NHRA take an active role in world record setting. USAC has its own team of timers and technical officials, while NHRA usually relies on the expertise of the Southern California Timing Association (SCTA). SCCA and PSC (formerly IMSA) have also sanctioned land speed record attempts.
To certify a record setting course, extreme care is taken to measure distances for the speed traps, usually one mile and one kilometer in length, so that each run taken will time the vehicle at each distance. To establish a record it is required that a competitor make two passes - up and down the course - within a one hour period. The record is an average of the two directions.
so, perhaps for someone to be able to consider themself a 591 vaulter or 6m vaulter or whatever height vaulter wants to identify himself as the height must be the average of their two highest jumps. so tim mack is not a 601 vaulter, but a 598 vaulter.