Change item: Supplementary signature means: change, addition. Due to changes in design and construction, the contents of the original contract are as follows: the above changes and additional project payments will be settled together with the final accounts of this project. The original project and specific practices may change during the implementation process, which is called project change. Basic introduction: There are two ways to change the project: supplement and modification. Supplement is the addition of new content to the original contract, thereby creating a new creditor-debt relationship.