Hi,
Could it be that when you change the % you are not hitting the Finish button and the Publish button? When you return to your screen you have to wait a bit until it's done publishing and refreshing the page.
It could also be the amount of information you have on your left section. If it's a grid, the width of the fields and columns will be enough to fit the caption regardless of how small you make it; so look into reducing the characters of your captions maybe.
The best way to diagnose your issue is if you send us a screenshot maybe.
Marwan