This section enables a Vault Manager to choose which rule sets (if any) to impose on investment subscriptions. In order to add any of these rule sets, go to the Policies tab on your Vault Manager launchpad. These rules are the same discussed in the setup section here.
If you want to limit which addresses can subscribe to your Vault, you can opt to have a whitelist policy. This is a list of addresses you curate which dictate who can invest in your product.
This allows Vault Managers to select minimum or maximum investment amount that can be invested into the product. The amount is always expressed in the Vault's denomination asset.