For images in the “Upload and Annotate Image” question panel (see below), you can only write/annotate on the dimensions of the background image, not the panel itself.
Even if the panel is full screen and looks like it has a wide white background, such as this:
If the background image has smaller dimensions (such as width), this becomes the area available for annotation (ie. a considerably smaller area when in Answer mode for students):
There are a couple potential workarounds to address this and add some extra workable space to the image. One is to simply take a screenshot of the image in Lt in Preview or Edit mode (like in the second screenshot) and replace that in the annotate panel. You could also add the image to a PowerPoint or Google Slides with a white background and export the entire slide as an image.
For additional assistance with Lt, please contact your local ADInstruments Technical Support Representative.