10DLC throughput is managed at a brand or campaign level, so it's not generally required to use more than one number for your campaign.
However, there may be some use cases that require multiple numbers. If you intend to use more than 50 numbers for your 10DLC campaign, then you must set up a number pool. Reach out to your Sinch Account Manager for assistance in requesting and configuring a number pool for your 10DLC campaign.