Delays in transitioning between Workflow States

Hi There

I have a workflow that is supposed to transition between states with a delay.

This is the workflow transition

However, according to the workflow history, this moved between the states in 1 & a 1/2 hour:

Is my understanding correct that, based on the transition set up, this should move from State 1 to State 2 after a 1 hour delay?

Why would it move in 1.5 hours?

In State 1, there is a single workflow action:

That has a scheduled delay of 0 hours.

Is 0 hours equivalent to 30 minutes for the purposes of the workflow?

thanks