For private company employees posting total comp on Levels, what formula are people using to value their equity? For example, with ISOs, does everyone somehow know the price per share that investors are paying in order to calculate the delta between that and their option strike price?

For example, if I've been granted 10k ISOs at a $10 strike, and the current 409a is $10, my equity is worth $0/yr. In order for those options to have any hypothetical value, the FMV would have to have risen since my equity grant took place. 

Given this, it feels like equity numbers across the board should trend much lower on the site than they do, or else I've really gotten shafted at my last 2 companies