If these are RAW files, then it is better to set black and white points in ACR. If you Shift open the processed RAW file to open as a Smart object, these settings are non destructive, and editable.
Setting black and white points by the numbers in Photoshop is risky, because no two images are the same. You might want to block out noisy shadows, or ignore specular highlights, and set white point to a more meaningful part of the image. So if you really want to sort out these points inside Photoshop, a better approach might be to use a Levels Adjustment layer, and hold down the Alp (Opt) key while dragging the black and white sliders. This puts the image in Threshold mode, so you can see exactly what parts of the image are being clipped, as well as which channels, or combination of channels are being clipped.
But using ACR is a no brainer. You have the full image bit depth to play with for a start.
I appreciate your advice Trevor. But still, i need to understand these clip numbers. I edit thousands of pictures, and i need to work fast. I want to use it as an auto function. It is going to be within action steps. I want to enchance contrast by clipping white and blacks, and it has to be a subtle adjustment. I want to get at least one pixel pure black and one pure white.No more than that. Which number makes sure that at least one pixel of black clips?