Hello, hope you are doing well!

Its fine if you have entered best of 5 subject marks and total 500 marks. There is no mistake in that. Usually best of 5 or 4 subjects are asked and not all subjects. But if your college asks for all 6 subjects marks you can tell them about it when you verify your documents at the time of admission. For this your application won't be cancelled. Your actual document verification will be done at the time of admission. So, relax its all fine. You have not committed any mistake.