The source for this data is the spreadsheet named Thread.xls, located in the Design Data\XLS\<localization>\ folder. If you don't know where this is, look in your application options > File tab, and also in your Project (which can overrule the application options).
Typically, thread callouts are pulling from the Custom Thread Designation column, so you could customize your Thread.xls spreadsheet by making it read the way you want. As you will see in the spreadsheet, there are a variety of pitches and classes for each thread size, so you could even delete all the extra choices that you don't use, leaving one of each size. Or, add a sheet (and make it Sort Order - 1) with just your selections.
Hope that helps,
