When you choose one of the installed hard drives to be used as a Global Hot Spare under Intel® RAID Web Console greater than version 2.34 you will see two further options, No Affinity and With Affinity, as per screenshot below:
This allows the Global Hot Spare to have the ability to be used as a spare for any of the Virtual Drives being controlled by that controller, regardless of location.
This sets the Global Hot Spare to have an affinity with the enclosure in which it is located. What this means is that this disk will ONLY act as a Global Hot Spare for Virtual Drives that are located within the same enclosure as itself. This disk will not function as a Global Hot Spare for Virtual Drives that are outside of its own enclosure.