Documentation
Configuration - Objects - Admin Resources

It is always possible to change a resource, but keep in mind that this can affect existing reservations. To ensure availability is calculated correctly, you need to update the resources after modifying an existing resource. You can do this quickly and easily with the bulk action 'Update resources'. When using the bulk action you can update multiple already existing reservations at once, it is also possible to do this per reservation via the action link 'Show resources'.

Updating resources is also necessary when adding a new resource and linking it to an existing product for which reservations have already been made!