Tubing in OPPID

Hello, i would like to know how to implement tubing into OPPID. I´ve tried to add ex: OD 6.35  in Class Editor as a pipe size in the OpenPLANT PID 1.07>Lists>Metric Pipe Sizes scheme but it only accepts whole numbers. If someone could please refer me to any tutorial or guide about how to implement this type of pipe sizes i would really appreciate it.