When setting background images in Customizer there is a hint like this: left top, x% y%, xpos ypos (px).
It makes sense to us but not to the clients. I would like to modify it but unfortunately it’s not translatable. Maybe add in multilingual support for this string in 1.5.6?
Also, we’ve merged all of the translations into one gp-premium.pot file in GPP 1.6, so I would definitely suggest checking out the beta when we release it, as some of your translations might need updating 🙂