It means that if the score between A and B is 25: 17,
25:20,
At 25:20, the big score was 3: 0, the small score was 75: 57, and the net win was 18.
The score between B and C is 25: 15.
25: 15,
At 25: 20, the big score was 3: 0, the small score was 75:50, and the net victory was 25.
Similarly, if the net score of C over A is 13, then B comes first, A comes second and C comes third.
However, the big score of the game that must be won by three teams is 3: 0, 3: 1 or 3: 2 ... in order to calculate the net winning score.
2 If A wins B3-0,
B wins C3: 1
C wins 3: 2, so A comes first, C comes second and B comes third. Look at the net victory
Before the competition, the organizing committee has rules, and the rules are the basis for the execution of the competition, which write the handling methods of problems in the course of the competition, which is an agreement that everyone should abide by. Or do it in accordance with international practice.
I hope it helps.