I'm not familiar with that set, but I have seen this solved in a number of ways.
Sometimes there's a fret map that has the pieces numbered, if not on the fret.
Sometimes those numbers match the kit part numbers.
Sometimes there's a scrap of paper that gives a conversion chart for fret numbers/ part numbers.
Or like you say, you may have to just guess.
If you do and are successful, do share.
Makes GMM look pretty good, eh?