You do not need to predict which team wins. You only care about total combined goals scored.
Over 2.5 wins with 3, 4, 5+ total goals (e.g., 2-1, 3-0, 2-2). Under 2.5 wins with 0, 1, or 2 total goals (e.g., 0-0, 1-0, 1-1, 2-0).
You pick Over 2.5 in Real Madrid vs Sevilla. Game ends 2-1 (3 goals). Over 2.5 wins!