ERROR IN TRY

Hello Victor,
the problem is that you changed the group settings from initialize to delete (one of the last sildes). With initialize the groups were generated in the first place, please do not remove that option.
I assume that you want to simulate the emptying of the hopper - and if it is open at the bottom, the particles will be deleted when leaving the simulation domain anyways. The delete command you used can would remove the entire group (which was not initialized in your case) right when applied (which would be before the first run in case of this simulation).
When you want to delete particles after a certain time you would have to do this in a derived simulation.
Cheers,
Alice

Hello Victor,
the error message is telling you, what the issue is: you imported a mesh, which is neither used for insertion nor as wall. Since the silo is defined as wall, I assume that the insertion face is not used during the insert command.
Concerning the units: on the x-axis you have the time step, on the y-axis you always have the unit that matches the displayed graphs (can be more than one at a time).
Cheers,
Alice