Starting time at half an hour

Hello everyone!
I use this component for one big site and i think it’s one of the best I 've use on joomla!

I have one problem.
I would like to se the starting time at 8:30 instead of 8:00, but i don’t know what write in the specific field in the template section of the back-end.

With 8.30 the field turns in red, with 8:30 turns in red, with 8,30 turns in red.

Can you help me please?

Thank you!