Was just paid 1 week early and an additional ~$500 on top of my regular salary

Location: Chicago, IL

Very very confused right now. Unfortunately an automatic payment took $20 of the total amount (which is how I noticed in the first place). I'm not trying to owe my job a debt I can't pay back. But if I can keep the funds (assuming not) it would be an immense help to me. Looking for the best way to move forward with this.