Amateur boxing is scored differently than professional boxing.
Amateur can be a judges decision, or a referee decision.
Or counted by how many 'clean' blows are scored.

Professional Boxing is scored by amount of points a boxer receives in a bout.
You can receive a maximum of ten points in a round.
If round is boxed evenly or no clear winner is scored 10-10
Fighter A wins the round 10-9
Fighter B wins the round 9-10

Fighter A wins the round and scores a knockdown (fighter B receives a standing count or is knocked down), round is scored 10-8
Fighter B loses a point for getting knocked down
Referee can discount a knockdown if it is ruled a slip, or unfair punch, headbutt or thrown to the ground.

10-10,10-9,10-8 are most common scores
But you could see, 9-9, 9-8, 10-7 but these are very rare

3 round fight
Fighter A wins fist round
Fighter B wins second round a scores a knockdown
Fighter A wins third round, but fighter B scores a knockdown.
Scores would be
Round (1) 10-9
Round (2) 8-10
Round (3) 9-9
Total Fighter A(10+8+9) = 27
Total Fighter B(9+10+9) = 28
27-28
Fighter B wins by one point.