Runtime Errors are generally caused when a conflict between the Techno CNC Interface and the Windows operating system occur.

Runtime Error 6: Overflow

Cause: In older versions of the software, this can be caused when G Code calls for a very high tool number (i.e. 253).

Solution: Change your toolpath settings to use a lower tool number (i.e. 5) or upgrade to the latest version of the Techno CNC Interface at  support.technocnc.com.