Find number abc

The boss ordered one of his men to dig a hole eight feet deep. After the job was completed the boss returned and explained an error had been made and the hole wouldn't be needed. "Fill 'er up," he ordered.
The worker did as he'd been told. But he ran into a problem. He couldn't get all the dirt packed back into the hole without leaving amound on top. He went to the office and explained his problem.
The boss snorted. "Honestly! The kind of help you get these days! There's obviously only one thing to do. You'll have to dig that hole deeper!"