Currently each share is has a market value of $4.50.
They get 3 shares for every 2 shares. The 3 shares are worth 3 x $3.644 The 2 shares are worth 2 x $4.50. So the gain made on every 2 shares is the difference.
The gain per share is this divided by 2.
The percentage gain is the gain per share divided by the current MV.