It means that 100 is 5.0, and your average score is converted into 5.0.
The conversion method of each school is not exactly the same. Some schools have a full score of 5.0, and some have a full score of 4.0, which should be weighted and averaged according to each science score. You should consult the academic affairs office of your school to see if they have an algorithm. My own school doesn't count, but I have to go online and refer to other people's algorithms to calculate.