GS New Analyst application trouble

Hi everyone, I have some doubts about the applications for New Analyst in Goldman Sachs (EMEA). I hope you can answer my questions.

I'm studying in Italy and we have a different scale for grades: from 18 to 30 for exams. We also have a final grade for the degree that consider both the average and the thesis.

1) How I can calculate my "cumulative degree result"? The FAQs state:
Calculate the percentage range that reflects the average marks across all of your subjects taken in the previous academic year. Remember you will be asked to verify this percentage by providing your academic results.

Do I have only to convert my Italian average (the maximum is 30) of last academic year in a percentage (i.e. 30/30 correspond to 100%)?

2) About the academic transcript they say

Italy - university (including GPA) and high school grade transcripts

I read that there isn't a clear rule for conversion and often is better to submit the average before conversion. Should I send the "italian average" or try to do the conversion?

In regard to high school grade, is it enough to send only the final grade (we have a final grade also for the high school) or I have to send the grades for each subject that I got in the final semester?

Thank you in adavance!