The example below, which is reproduced from ASC 606, illustrates a contract with an option for additional goods or services that is akin to a marketing offer and thus does not represent a material right.
ASC 606-10-25-2 and ASC 606-10-55-42.
A material right arises from pricing on an option to acquire additional goods or services in the future that would not have been received if the initial contract had not been entered into. In such cases, the customer with the option has essentially prepaid for the future purchase.
Quoted from Implementation Q&A 14.