Time of Use - Flexible app. How to set non-integer start/end hours?

A query about the ‘Time of Use - flexible’ app on emoncms…
It does not seem possible to configure the tariff tier start/end times to be anything other than whole hours? Is that right? How can I set a ‘Night’ rate to run from 23:30 to 05:30? (Octopus Intelligent Go).

Yes, I know it still won’t be accurate if Octopus schedule an EV charge outside of their normal cheap rate period, but it will be good enough for my purposes.