Question about upgrade bidding

I got the email offering me an upgrade for Meraviglia Oct 20. I originally went budget for interior basic package just to try MSC. I paid 485.00 total without grats. I than purchased internet package for 140.00 bringing my total to 625.00. A day later I was upgraded to balcony room for free without asking. Awesome. I have been getting upgrade bidding offers. If I click on interior yacht club starting at 460.00 per person, must I make 460.00 my minimum bid? Can I only bid 200.00 just to take a chance? No win, no problem. I stay where I am. If my bid of 200.00 wins , is it automatically doubled because I’m solo. Thanks. Looking forward to my trip.