User bills expenses as part of the contract amount and has checked the project rule Include billable expenses in the contract amount. How to charge some of the expenses on top of the contract?
Core includes expenses as part of the contract if you un-check their Extra flag and excludes them from the contract if you check the flag. By default, the expenses are not included in the contract and their Extra flag is checked. However, the project rule Include billable expenses in the contract amount includes the expenses in the contract by keeping the flag un-checked. So if you want some of the expenses to be outside of the contract while the project rule is active, you should check their Extra flag. Check the Core Help for more on this field.