The Unlimited plan is absolutely unlimited, you can trade or update orders as much as you want without any limitation.
Unlimited plans are offered for 1, 3, 10, 25 or more Slaves. The packs can be combined together. For instance, if you need 2 Slaves, you can buy 2 packs of 1 Slave. If you need 13 Slaves, you can buy a pack of 3 and a pack of 10 etc.