其实这是所有格的省略用法，即省略了所有格的撇号，原句相当于：

The dog clocked a tremendous 27.47 secs for the 450 metres' trip.

又如下面各句的days, months, minutes也属省略了撇号的所有格：

In a few days time the sprouts will be ready to eat. 再过几天球芽甘蓝就可以吃了。

After six months training, the whole team is in superb form. 全队经过六个月的训练竞技状态极佳。

It’s very central, just five minutes walk from the main square. 那地方位于市中心，从主广场走过去只需五分钟。