^^ It's mostly not the first trial.

Micromouse competitions usually span multiple rounds, and in each round, the mouse maps the maze and keeps it in memory.
The run that counts is the one after the mouse has mapped the whole maze and probably optimized the route.

in free run competitions, the number of trials may be unlimited. In more mainstream competitions, the number of trials might be limited.
But still, the one you see in the video most certainly is not the first trial! 😀

#-Link-Snipped-#
1. Each contesting Micromouse is allocated a total of 10 minutes of access to
the maze from the moment the contest administrator acknowledges the
contestant(s) and grants access to the maze. Any time used to adjust a
mouse between runs is included in the 10 minutes. Each run (from the start
cell to the center zone) in which a mouse successfully reaches the
destination square is given a run time. The minimum run time shall be the
mouse’s official time.