Know which records you are viewing
A timer left running after the session actually ended overstates the duration you meant to record. Stop the active timer first so there is a completed record to edit.
Make the smallest useful change
Find that newest record in the Journal tab and choose Edit times. Set the end to the actual known finishing time, ensuring that its date is correct and follows the start.
Each completed record has its own start and end. A valid correction keeps end at or after start and no later than now; a running session instead uses its stored start and the current clock.
Verify the result
If you only remember a rough time, explain that in the note. A clearly marked estimate communicates more than a very precise-looking duration created from uncertain memory.
Preserve an honest history
Do not shorten another record to compensate for the mistake. Correct the affected session directly so each start-and-end pair keeps its own meaning.
Fastly is a lifestyle timer and journal. These notes explain the app and offer reflection prompts. They are not medical advice or a prescribed eating schedule.