Please write a new owner and his/her ownership on a new line with the format:
Name - Percentage of Ownership
The best way to do this is just calculating how much value/resources/time each co-founder can contribute. However, splitting up a company is more art than science. Don't be against giving away your company. A shareholder who owns a lot of the company will feel a lot more responsible for the work. It's better to own 30% of 1M than 0% of nothing.