exact RAM figures

Hi,

Is it accurate for me to do : 2100 * 16 == 33,600 bytes.

In the Bangle's case, yes. Some boards can get away with slightly smaller variables

Max memory usage for Javascript space is 33600?

yes

Its true bangle.js has 64 * 1000 bytes or 64 * 1024 bytes ram?

Yep. 64 * 1024

Does it make sense to take 64,000 - 33,600 = 30,400. And claim 30400 bytes are set aside for the firmware(espruino) to use, outside of Javascript?

That's right. There's the firmware, but also the execution stack, and the Bluetooth code reserves a bit too.

If I'm honest I'd have thought that we could get away with reserving a bit more for JS than just 33.6k though