You're confused. It refers to the price of all available shares. We don't say "The size of Meta shrunk in one day by 20%" because the share price fluctuated. That would be retarded. No one refers to the 'size' of a company is referring to market cap.
Your presumtion of others' inability to understand is making you confused. No one said market cap equals size of a company. But market cap does measure financial power if we talk about percentage of shares owned. Anyway no single private entity should have that amount of market cap.
> No one refers to the 'size' of a company is referring to market cap.
Saying a company is "the largest by market cap" is very common. Just saying "largest" on its own is ambiguous. "Largest by revenue" is also very common.
