A short call appears as an hour in your calendar. Before moving other appointments, open the event and read its start and end. The duration offered when creating an event is a starting value, not a decision about how long your meeting should last.
Set a useful starting duration
In Google Calendar on Android, open Menu, Settings and General, then find Default event duration. Google describes this as the time span for new events. Choose an available value that matches your ordinary work. Do not assume that changing this preference rewrites invitations or existing appointments.
For a fictional call starting at 14:10 and lasting twenty minutes, the intended end is 14:30. Check both fields before saving. If the offered duration is different, edit this event’s end rather than accepting it automatically.
Do not measure a meeting by its drawn box
Calendar also has a display option that makes entries shorter than thirty minutes appear as large as thirty-minute entries. That makes small items easier to see; use the actual event times to determine duration.
Create a harmless test event without guests and reopen it after saving. Check the date, calendar, start and end. If you later need to correct a recurring meeting, inspect whether the editor applies the change to one occurrence or a series before confirming.
Keep the other checks separate
A correct duration does not establish that a reminder is enabled or that a travelling guest sees the intended local time. Review those settings separately. These instructions concern the Android Google Calendar app; other clients and account types may offer different controls.