He said they also seemed to think their fingers were shorter than their true lengths.

他还说，大家似乎还认为自己的手指比实际长度短。

In other words, meaning the shorter the segments used to measure, the longer the measurement of the curved line becomes and the closer you get to the curved line's true length.

换句话说，用来测量的线段越短，曲线的测量就变得越长，也就越接近曲线的真实长度。