11 points
Companies such as Fidelity give an estimate on how much they are value after analyzing the finances of the company I think.
16 points
Fidelity does this because they invested in Twitter alongside Musk, and as a bank they are required by law to disclose the current value of their assets. They come up with a value of their stake, then the rest of us divide that by the percentage Fidelity owns to get the value of the company.