Use a timed work interval to define a finishable task rather than just watching a countdown.
Use the Pomodoro & Countdown alongside this illustrative example.
A practical example
For one work interval, choose a task such as drafting an email outline instead of a vague goal like finish the project. At the break, record whether the outline is usable and what interrupted you. Adjust the next task’s size before changing the timer duration.
Check the result
Test timer behaviour on your device before relying on it, especially when the screen sleeps or the tab is in the background. Browser audio permissions and power saving can affect what you hear.
Try a comparison
Compare one session with a single written task against one with several unrelated tasks. Note interruptions and unfinished work yourself; the timer does not measure those. Use the observation to make the next task more specific rather than treating the clock as a performance grade.
What this does not establish
A browser timer is not a guaranteed notification service and does not measure productivity. Keep the task record yourself if you want to compare sessions across days.