Why the hell we've been sold 100psi pumps for is another mystery too :

Here's how to change settings, provided by DJW
With the Varistream switched on - press+ and- buttons together for three seconds to display pressure setting
Release the buttons for 1-2 seconds then press together again for three seconds and the digit will flash
Use the + and - buttons to set a higher or lower pressure (best to adjust one letter at a time and avoid large swings in pressure)
Once the desired letter is displayed turn off the Varistream
When you switch back on it will have accepted the new setting. To confirm press both buttons together for three seconds and release.
Sounds complicated but in reality it's easy.
Oh, and the light, green= pump running,green flashing=low battery,red=pressure shut off achieved.
Tony