Sorry to be nit-picking, but the percentage of shares issued that the departed cofounder holds after 4 years would be 20%. It's not helpful to look at percentag

Sorry to be nit-picking, but the percentage of shares issued that the departed cofounder holds after 4 years would be 20%. It's not helpful to look at percentages during the calculation: look at absolute number of shares. If 1 share vests each month, the remaining founder has 48 after 4 years, the departed one retains 12, hence 20%. Of course, this ignores any further shares the remainin founder might issue to himself by investing his own money or assets (he holds a majority stake, so that shouldn't be too difficult)