How does FBA Capacity limit increase applies?

Can someone explain how “Request additional FBA capacity” system works, please?

I need to send my next shipment to FBA from overseas, but the QTY I try to submit exceed my allowed capacity limit (by ~200 sqft).

There two confusing attributes:

1. Period – if I creating shipment now (January), to be shipped later this month and delivered in March, what month should I select for my request (Jan, Feb, or Mar)? And do I need to enter multiple requests for further months?

2. How the bidding works? Should I enter just random number here?