Welcome to the forum... The priority codes for retail orders are usually just a number and they would range from 3 to 19, and 99. Priority codes 1 and 2 would be set by the Ford Regional Rep, so not something your dealer would assign.
Is your order a retail order or a fleet order? The fleet orders are typically where you would see that priority code and I believe K4 indicates the 4th week of October for when this would need to be built.
Here's a bit on fleet orders from a guide that's a few years old (2015) so some of this may have changed.
Fleet orders are prioritized based on a two-digit alpha-numeric priority code which indicates the month and the week an order needs to be built. Numeric priority codes (including 99) are not valid Fleet priority codes. See the Fleet Priority Code Calendar link below for valid priority codes. Please be aware of the following:
First available priority codes are calculated weekly based on current order bank, available allocation, controlled commodities, and plant downtime. It is very important to review the Fleet DNB weekly as first available priority codes can sometimes change drastically if, for example, there is a large influx of orders received.
Fleet receives a pre-determined amount of allocation (production slots) each month for weekly scheduling. Once the amount of orders prioritized for that week/month exceeds the available allocation, the first available priority code is moved out to the next weeWmonth.
Orders are selected for scheduling based on priority code first, then by order receipt date. Despite how long an order has been in the unscheduled order bank, if the plant is not yet filling the production week associated with the requested priority code, the order will remain unscheduled.
As a general rule of thumb, production dates are at least one month out from order receipt date. Every effort is made to accurately estimate the lead times, and to reflect longer lead times of specific conmodities. In the absence of adjusted lead times for commodities, please use the high, medium, or low risk rating as a guide.