The exposed photos on the camera are not bad. But when I opened it on the computer, I felt a little underexposed.

Your camera's screen display resolution is not as high as your computer's, and its brightness is different from your computer's, so your vision is different. Whether you are underexposed or not depends on the quality of the photos you take, whether all the lines are clear and all the details are clear. If both are not clear, the camera display is too bright to give you the illusion.

The photographer's skill is to master this difference and make the photos taken by the camera meet the needs. However, if it is slightly insufficient, you can simply do it with PS and adjust the exposure.