Flat numbering system help

Hi all, moving to Edinburgh next week and am trying to purchase broadband in advance. I know my flat address is 16/3F1 but on BT’s website, it only has 16 and then flat numbers up to flat 9. There are 3 flats on each floor so am assuming mine would be flat 7, but how can I be sure?

Sorry if this is a dumb question!

Cheers