Here I've collected only the athletes who broke ten minutes, and as you can see, Hirayama's record is the slowest among the five.
Literal
Here [at-では] 10-minutes [obj-を] cut athletes only [obj-を] gathered [copula-のですが], seeing [gen-の] as Hirayama [gen-の] record [topic-は] 5-people [gen-の] inside [in-で] most slow record [copula-です].
１０分を切る 'to break / cut under ten minutes' uses 切る in its 'break below a threshold' sense. のみ is the formal equivalent of だけ 'only.' 見ての通り 'as you can see' is a set phrase (見る + て + の + 通り). The structure のですが provides explanatory background before presenting the main observation.