Delay not accepting fraction of hours?

Delay not accepting fraction of hours?

Hi,
I have a simple flow, triggered by submit in a form.
I set delay of 7.5 hours & then 16.5 hours each one sendingme an email.
Having reviewed the flows, I see that the durations was just 10 hours, which confused me?
I have to assume that 7.5 hours is read as 5 hours and 16.5 hours is also read as 5 hours?.
I have changed the times to 8 hours and 16 hours and await the next trigger.
Can someone confirm this is the case as I cannot find any reference to setting fractions in setting time delays in help.