I did not understand it either but if you look at how all the harrisonson were made that was how that are listed. Example. 3 core 2 row, 4 core 3 row, 4 core 4 row.

They are remaking most of the tanks now with the correct markings here in the us. Here is a link to all the ones.

http://www.heartbeatcitycamaro.com/store/category/7/270/Radiators%2C-Harrison/

I would like to find out id our was a 4 row or a 3 row but seems no one knows.