[unity3d] the font size is adjusted to the maximum value, which is still very small / the canvas aspect ratio is very large

Problem description
The subject originally intended to add subtitles, which will be displayed at the bottom of the screen after triggering. However, when adjusting the canvas size, it is found that no matter how to adjust its aspect ratio with rect tool, its size changes from the world perspective, but the actual size does not change. As shown in the figure below:

As a result, the subtitles under the canvas can not be seen in the camera even if the font size is adjusted to 300.

terms of settlement

Although we manually adjusted the canvas size with rect tool, we didn’t check the canvas scaler, as shown in the figure below. After checking, the canvas urinates normally.