Make a payment that will bring you under your credit limit the further the better. How long have had the account with Discover?
I might be misunderstanding the title and your question. Are you asking about the consequences of going over limit, impacting graduation from secured to unsecured?
I can't speak to the graduation part, but with my unsecured disco I accidentally went over limit by around $30 or so. I thought my payment posted before it actually had. I called the CSR in a mild panic, and was assured that nothing bad would happen, I just wouldn't be able to use the card further until payment posted. It was never reported to bureaus, never incurred any fee or any consequence I'm aware of.