There was a very brief mention in the video, but this link goes into more detail: https://micromouseonline.com/micromouse-book/rules/. The score of each run factors in 1/30th of the time spent to search. There is a separate period where the mouse can search, and then it goes through the maze at high speed using the route it planned prior. Obviously if you spend a massive amount of time searching, that will impact your score but it seems to prioritize the later, faster runs in terms of scoring.