Burst speed vs. sustained speed
Shorter tests usually produce higher scores because you can hold full concentration for the whole run. That makes a 30-second test ideal for warming up and for seeing your peak speed. If you want a number to put on a CV, use the one- or two-minute test instead, as those reflect a pace you can maintain.
Frequently asked questions
Why is my 30 second score higher than my 1 minute score?
Short tests measure burst speed. Fatigue and lapses in focus have less time to slow you down.