You probably figured it out yourself by now, but maybe some other people find this useful. I think the format you're looking for would simply be h:mmt
The curly brackets are from an old version of the FullCalendar plugin the widget is based on and should not be needed anymore
See also the following:
https://fullcalendar.io/docs/text/timeFormat/
https://fullcalendar.io/docs/utilities/date_formatting_string/
https://fullcalendar.io/docs/utilities/formatRange/