You can now edit the the Tools Catalog Fastener data:
Go to C:\Program Files\IronCAD\2021\AppData\en-us
Unzip the FastenerData.zip file to the folder: C:\Program Files\IronCAD\2021\AppData\en-us\FastenerData
Edit the text files inside C:\Program Files\IronCAD\2021\AppData\en-us\FastenerData to edit the sizes.