you need to take some time and learn how to use the manual that you bought from midwest manuals. guidance and advise isnt something you will get from those guys, but hey, you saved a few bucks.
in previous conversations, i have asked exactly what manual you are referencing. i believe i even mentioned where to find the number. its in there, you just need to browse it more thoroughly.
just taking a guess, but i believe your referencing lit#12618-SM-00. you may also have the supplement #8CT-28197-11. this supplement basically covers items that may be specific to your machine and year. most of the main manual covers several different models with illustrations particular to your machine, if necessary, as alot of the info for clutch, suspension and misc is the same as other models for several years.
your confusion is coming from the references to the 500 and 600 models prior to 2000. in 2000, the 600 became a triple. its simple to look at the illustrations and see that they are referencing a twin cylinder engine, usually followed by an illustration for the 700 triple.
if you recall from some of our past conversations, i mentioned that the 600 is an identical engine to the 700, just a smaller bore. with this concept in mind, most anything in your manual pertaining to the triple 700 engine applies to your 600 triple, with the exceptions of clutching, gearing, high altitude tuning, and carb tuning.
to answer your question, the ring gap is .35mm-.55mm. i would be more than happy to familiarize you with your manual so that you can get more enjoyment from it. the info is in there, you just need to filter it.