No... I'm pretty sure you can not edit that, you also can't edit things like Wealth either...
You can however instant fill up a ship with supplies using SM so you do not have to be completely restricted to your starting amount of supplies for role-play reasons.
You can also if you are so inclined edit the database directly and then you can edit things like supplies, wealth and allot of other stuff, just beware that you can't submit bugs if you edit the database.