A family of Microsoft word processing software products for creating web, email, and print documents.
Your comment about changing the justification (actually the paragraph alignment, which is apparently set to Centered in the Paragraph settings of the Caption style) is correct. The only way to have the complete Figure and number appear in the dialog is to change the Caption style's paragraph setting to have Left alignment.
If you do this when you start adding captions to the document, the Figure and number will always appear at the left edge of the box. When you've entered all the captions, you can change the Caption style back to using Centered alignment, and all the captions will immediately change to being centered.