In case you want to subtract 6 natural days from "Due Date", you have to use post-function Mathematical and date-time expression calculator with the following configuration:
Text to be parsed is: {12200}-6*{DAY}
Notice that:
Once configured, transition "Create Issue" will look like this:
In case you want to subtract 6 work days from "Due Date", you have to use post-function Mathematical and date-time expression calculator with the following configuration:
Text to be parsed is: addDaysSkippingWeekends({12200},-6,LOCAL)
Note that:
Once configured, transition "Create Issue" will look like this:
Since version 2.2.39, Jira Workflow Toolbox supports Custom Schedules, and you can do all you are doing now using addTimeSkippingWeekends() and subtractDatesSkippingWeekends() functions, and much more.