What likely happened to BSP versions 1-16?

[Valina35]

the oldest bsp version files we have in leak and any other source game is bsp 17 so i wonder what likely happened to earlier ones, is it possible that valve just started directly on bsp 17 or is it likely they started on bsp version 1 and updated it as bsp format was updated and since we dont have any earlier compiled maps its why the earliest we have is bsp 17

[homosapien1t]

BSP version 17 is obviously a reference to City 17, mystery solved

But most likely, they might have randomly chosen 17 or something close when they switched from .map to .vmf (Valve Map Format) in 2000.