I have InDesign CS6, but I think the differences are not so serious.
1. It depends on the setting in Edit > Preferences > Units & Increments.
If your ruler units setting is e.g. "cm", you can use numbers without units for cm dimensions, for all other measurement systems you have to put in the number + unit.
2. The brown border is for the image, the blue border is the frame.
Use these icons to adjust the frame or the image:
Once you have enlarge the photo numerically with the content grabber, you can use the Fit Frame to Content button, menu Object > Fitting > Fit Frame to Content, or the keyboard shortcut (option+command C [on a mac]) to enlarge the frame to match.
Thanks for your help.
Unfortunately putting in a measurement using the content grabber and then resizing the frame to the content adds more steps that it saves (putting in a measurement in the percentage box and adding the unit then). I just want to put the measurement (as a number) in and have it resize the content and the frame in one step.
I'm assuming that it's not possible as no-one else has suggested an answer to that. Oh well - it's only a small thing.
Again, thank you for your help.
Thanks premio_oscar - that did it!