If you have a linked record field linking to your “seats” table, you can configure the linked record field to only show you a list of the seats that haven’t been chosen yet.
Beyond that, Airtable forms do not have the ability to display any dynamic information onscreen (such as calculations or formulas or lookup fields), so you would need to turn to an external form tool to do this for you:
1. JotForm offers the ability to create seating maps with limited seats to choose from, You would send your form submissions from JotForm to Airtable using Make.
2. Fillout creates forms that communicate live with Airtable, and it can display calculations onscreen or disolay dynamic information from Airtable onscreen.
p.s. If you have a budget for your project and you’d like to hire an expert Airtable consultant to help you with any of this, please feel free to contact me through my website: Airtable consulting — ScottWorld