I didn't see clearly what you were trying to express, whether you want to mark numbers and write magnification in the lower right corner of the picture or you want to mark them in the document.

If you want to add a mark to a picture, you can directly use PS or this simple drawing tool to solve it.

If you want to bid in the document, you can do it through special typesetting. If you are sure that all other formats have not changed, you can choose a picture as an embedding test, then add a space in front of the next line, and then enter numbers and multiples in the ideal position.