What a 3×3 scramble is for
A scramble takes a solved cube to an unknown position so that every solve starts from a fair, unplanned state. Because the same scramble applied to the same starting orientation always produces the same cube, two cubers who use it face exactly the same solve. That is what makes times and averages comparable.
Random-state, not just random turns
Twisting a cube 25 times at random sounds fair, but some positions come up far more often than others. A random-state generator instead chooses the final position evenly from all 43,252,003,274,489,856,000 possible positions, then works out a short move sequence that produces it.
Random-state is the approach the WCA uses for the 3×3. Cubeathon's scrambles come from cubing.js, an open-source cubing library that implements it, so they are WCA-style practice scrambles. Official competitions generate their scrambles with the WCA's own program.
Reading a 3×3 scramble
Hold the cube with white on top and green facing you, then apply the moves from left to right. A plain letter is a clockwise quarter turn of that face, a prime (') is counter-clockwise and a 2 is a half turn. 3×3 scrambles use only the six outer faces: no wide moves, slices or rotations.
If your cube doesn't match the preview, a move was missed or the cube was held differently. Replay the scramble move by move to find the spot.
Practising with a scramble
Scramble slowly and accurately; speed only matters once the timer starts. Then use the 15 seconds of inspection the way competitors do: find the cross and plan as many of its moves as you can before you start. Timing every scrambled solve is how you see whether your average is really improving.