Even out a run with short bursts
When a fast run in one hand comes out uneven, Short bursts puts a fermata on the first note of each beat of the run on the score and plays it to you once. You play one beat's notes in one go and stop on the next beat's first note: a stop every beat, then every other beat, then the run as written. Only the run's hand is listened to; the other hand can play along or rest.
After a take, choose Practice in short bursts
It's right under the button that polishes those bars in the result; if that button shows another drill, pick it from Other practice next to it. While you're practising a spot, Other practice in the bar at the bottom opens it too.
Listen once, then play two takes in bursts
The score shows a fermata on the first note of each beat of the run. Play one beat's notes in one go, stop on the next beat's first note for as long as you need, then go on from that note; the first take stops every beat, the second every other beat. The metronome stays off for these takes, since the stops have no set length, and the speed is the one you came in at: the app never raises it on its own, and you can change it yourself. After each take you see whether the notes were right and most bursts came out even between the stops, however long you stopped; if a burst came out uneven, the result says so and you play that take once more.
Play the run as written
The score goes back to how it's written, and this take carries on your practice of the spot at the same speed. Start short bursts again whenever you like, or simply keep repeating.
Playing a run a few notes at a time, with a stop between the groups, is a long-standing way teachers use to even out fast passages. Each group goes in one movement, the hand relaxes at the stop and gets ready for the next, and joining the groups a step at a time turns them back into the whole run, which playing it as written at the end confirms.