You filled out a W-4 for your job. Assuming you filled out normally with no additional withholding, it looks like you'd owe the IRS about $1,000 each year. The penalty can be 100% of the amount owed.
That's not the bad part. The bad part is dealing with the IRS. They'll send warnings and eventually garnish your wages if you don't resolve the matter.
Disclaimer: I'm not a tax professional. You need to talk to one. There may be an easier way out of this.