A 10 minute timer fits the jobs that are too big for a quick burst but too small to plan around: clearing an inbox, reviewing yesterday's notes, reading one section of a chapter, or a single practice set. It also makes a good warm-up before a longer session, because ten minutes of easy work gets you moving without wearing you out.
For younger students, ten minutes is a common length for one activity. A countdown they can see turns an abstract instruction into a finish line they can watch getting closer.
