I’m not sure this will reduce or increase confusion, but here goes: I spoke with Alison , who apparantly is a new hire to work with Sherri on the contracts. She said that contract numbers will not and do not change. If a contract holder drops out or a previously scheduled demo airframe is switched to a customer sale aircraft, there will be no change to contract (or position) numbers.
Actual serial numbers are issued in a one up fashion 1019, 1020, 1021,…) by the factory and are not in any way linked to the contract numbers.
For example (& I am sure these numbers are not correct) if contract holder #30 gets serial number 1027, then it stands that contract number 31 woul would get serial number 1028. However, if contract number 31 fell out, then contract number 31 would get serial number 1028, etc.