That is an interesting video because of that floating popup showing the size. I cannot figure out any options to make this show like it does on her machine. It is possible there is an option to show this but it may also be possible that a third party addin is required to provide this functionality. I note that the comments on the video show other users also don't have the popup showing and the video creator hasn't replied to their question.

As an alternative, I would recommend a better way to crop images to a common aspect ratio. If you click on the Crop dropdown, you can select from a range of cropping aspect ratios. Once you have made a ratio selection, you can then proportionally resize the cropping area by dragging a corner and/or resize/reposition the image by dragging. THEN use the size controls as the video shows around the 3:35 mark to get a specific width or height.

__________________
Andrew Lockton
Chrysalis Design, Melbourne Australia