How to understand the american grating specs ?

Welded steel bar grating is the most common type of grating in the world , We describe specs of grating in china with bearing bar size and pitch , crossing bar size and pitch , overal width and length(Span) , following is a picture ,which showing the details.

As know , American use INCH system , they discribe the gratings by inch ,for example , 1 X 3/16 -19-W-4 , this means bearing is 1inch x 3/16inch at 19/16 inch spacing , welded type , crossing bar 6mm twisted at 4 inch spacing(pitch) , normally crossing bar 6mm unless it is marked as 8mm or 10mm .