TLDR - the CEO was granted 1 million shares over 3 years at $5 per share. Now that GameStop's stock price went up due to the WSB frenzy, that stock is worth $170 million. He is departing earlier than expected, and per his contract he retains those shares but gives up a cash payout and another $50M in shares he could have had if GameStop's performance improved over the next few years.