500.00 richer!

So today I got my pay check and it was more money. So anyhow, I was like "why...why is it so much more?" anyhow after staring at it, I seen that my mid-month advance didn't come off. I did payroll and processed it so it looks like I did this on purpose. Anyhow, the owner came and I told her "you need to write me another check....this one doesn't have my advance off it" and she said "no I can't do that, the money is already gone"...and she left it at that....so I said "well I will bring you in 500.00 then" and she bascially told me to keep it and that she wouldn't have even noticed anyhow and left it there. I hate this. So I thought, its not 'my' 500.00. And I really, really don't like the idea of keeping it. I mean, 500.00. Its not like 20.00. Its a lot of money...to me, maybe *obviously* not to her. But she assured me "just keep it"...but it just isn't right...