In a private company, there's no "real" public valuation of a share, so an employee who has some kind of stake really only has two real options to dump their shares, either through a company buying it (cognition) or the company going public. Without either of these events, it's really difficult, even if there's no contract about it, to sell the shares.
So the value of the company took a nose dive in the private market through the hiring of windsurfs principals, and the employee either kept his shares and went with the company, or took a job with google. So the two values are:
1. Stay with Cognition and retain the private market shares of Windsurf and salary
2. Leave cognition, forfeit(?) the shares, get whatever salary google offered
So those are the payouts being compared.