The equipment that you use on your specific site is a major factor in the performance you can expect to see from a particular excavator.
One of the biggest factors in how useful a piece of equipment will be is the bucket capacity of the excavator you use.
This effectively means how much your excavator can carry in a single attempt. If you can hold more per scoop, then you can expect to move much more in a day.
Other factors affecting what a piece of equipment can do include the load-bearing weight of your equipment and the speed at which it moves, since this will change the number of buckets you can carry in a day.
As a standard amount, you can expect an excavator such as the Kubota U17-3a to move 40 cubic yards in an hour, but this will vary based on what you drive.
You can get a better idea of excavation rates by
doing your research
before hiring a particular machine.