Imperial bolt or plate sizes are incorrect in the connection dialogs.
These are steps to fix a problem where you see incorrect bolt diameters or flat bar sizes in a connection dialog.
See figures below.
1.) Go to the MicroStation Menu - Settings > Design File.
2.) In the dialog that opens select Working Units from the menu.
3.) Under Linear Units set Format to MU:SU (Master Unit, Subunit) and click OK.
4.) Go to the MicroStation menu and select File > Save Settings.
5.) Exit out of ProStructures and then reopen it.
6.) If you have a connection that still has incorrect bolts or plates use the connection command to delete the existing connection.
7.) Reapply the connection and it should have the correct plate and bolts.