All GM cars were built to a dealer order. The order could be for a specific customer, for dealer stock, or fleet for a leasing company.
For '69 the Camaro order form had a 6-character alpha-numeric code in the upper RH corner. For example in Jerry's 69 book one of the paperwork examples shows 'NDB065' on the shipper copy/window sticker. That was the form code. When Central Office confirmed production of the order to the dealer an order number was generated. In this example 117392, also stamped on the cars' body tag for tracking purposes at Fisher as there was no VIN assigned at that point. This number has no bearing on when a car was scheduled for production.
I believe only Chrysler built cars on spec in those days, hoping someone would take them. Lee Iacocca got rid of the "sales bank" there around 1980.