A home run is one hit, but can score several runs
Read a home run total separately from the team runs added on the play.
The hitter completes the bases
MLB defines a home run as a fair hit on which the batter scores without being put out or benefiting from an error. Most travel over the outfield fence in fair territory, but inside-the-park home runs also exist.
A home run is one hit in the hitter's record. It can produce more than one team run because runners already on base score too. The team run total is not simply a count of home-run swings.
The base situation changes the yield
In a hypothetical solo home run, only the batter scores: one run. With two runners already on base, that home run can score three. With the bases loaded, it can score four, commonly called a grand slam.
Those are worked examples, not reports of a current game. Do not add the hitter's one hit as another run after already counting everyone who scored. Hits and runs are different box-score columns.
Not every ball over a fence is fair
The fair-territory condition matters. The MLB glossary also describes cases involving the foul pole or a fielder contact before the ball clears the wall. Unusual plays need the actual ruling rather than a distance estimate.
On ScoreZaap, a score rise of four alone does not prove a grand slam. Read a confirmed event description before naming the play. The live score shows the team total; the source account explains how those runs arrived.