When you sign up for a NaaS subscription, the 10 STRNGR is a contribution, not a deposit. As stated on the Sign Up Now page:
A non-refundable and non-returnable contribution of 10 STRNGR to the StrongBlock community is required to sign up for a NaaS Subscription and participate in rewards. Your 10 STRNGR will be distributed as follows:
- 10% future use
- 90% to rewards and pools
Distribution subject to change over time.
The 10 STRNGR contributions cannot be returned, it is used to further the protocol. Selling a NaaS subscription is also not possible, a NaaS subscription is tied to your wallet.