This from the technical manual regarding the number at the start of the fourth line.
"Where the above sample shows a dash at the beginning of line 4, some cars have a 1 digit number or letter, presumably identifying additional body work for certain versions or options" but no mention of what each number or digit could mean.
I did some searches using the "search" tab, with "body plate" as the search string, searching only in the subject topic line. There was nothing I could find there definitive about the first number in the fourth line. There were references to options, with one person suggesting it was related to the radio.
I did one more search using "data plate" as the search string and found this from Hans in Sweden
"This is correct. There could be a "6" also. This "6" or a "0" were indicators for standard paint, light or dark pigmented. Hyphen were for mix of standard and metallic on a car(Hard Top vs. body)
/Hans in Sweden"