this is a good question. basically the total amount of shares are reserved for you (in the example - 50%)-no new shares are issued. in the article I provided our(Staply) vesting procedure-if I or my partner leaves the company, he gets a certain percentage of the total amount of shares in accordance with Vesting, other shares destroyed, so the stake of each remaining shareholder increases proportionally to the amount of destroyed shares. in the article you can find example of the statements. however, vesting is quite flexible procedure and you can easily put the procedure, described in your comment