The script has a few features.
On the left, taking advantage of the 8 pixels of dead zone, I have a speed visual that basically deconstructs what effect your current velocity has. Colors are used to denote target speed, and the left vertical bar shows how much of an 8 MPH threshold is filled. Tick marks are used for 1 MPH increments, but meeting these tick marks have no impact on the player's position. Filling the rectangles do, representing these 8 MPH thresholds.
As well, the console output is also used to spit out frame counts automatically (using register exec functions) on how long it took to complete each race. There is a disabled feature in this script that would also use this output for checkpoints, letting the TASer know when the player has hit the next segment of the track. Uncomment a line with LogCheckpoints() (under function BasicHUD) in it to activate.
Finally, the numbers display. Shame my memory of the script is basically nil on the details here, but so it goes. I recommend experimenting a bit, and if that isn't helping, open the script and look for my comments in BasicHUD. I do have a habit of using hexadecimal if the numbers line up better that way.