The Nominal Diameter does not match the information in the Specs Databases in OPM V8i

Hello! I work in OpenPlant Modeler v8i. 
The Nominal Diameter does not match the information in the Specs Databases.For example,I set the MAIN_SIZE as "15mm" in PIPE table,while the

Nominal Diameter displayed in OPM is "250".AS the pictures showed below:


I also checked the data type, but there is no problem.

If it is convenient, I can provide a database file.