Does BOSTES consider your internal marks in ATAR calculation or just ranks? Because everyone seems to just put ranks for ATAR estimate...
BOESTES (NESA) doesn't calculate your ATAR. That's determined by UAC.
UAC uses your raw assessment mark and raw exam mark to calculate your ATAR.
When people provide their ranks, the link between that and the ATAR is that you could estimate your final HSC mark from your rank if your school is relatively consistent each year, then the mark can be used to estimate the ATAR because UAC releases data correlating the HSC mark to the scaled mark (as in, the raw marks mentioned above are scaled - this is not your final HSC mark). Have a look at those online ATAR calculators.
However, I bet most people just literally guess an ATAR without much thought.