Right side article options is too small (backend)

-- HikaShop version -- : 2.3.5
-- Joomla version -- : 2.5.28

Hi, when I edit an article in the backend there's a left side and a right side, the right side containing all the options, characteristics, prices, et cetera. This site is very small, which causes for example the prices to be badly visible. The left side is 70% (I see it in the code) and in our case way too width. Is there a way to make this more in balance. Is there a line of CSS I could put in my custom css of the template or so that will change the left side to 60%. Or is there another solution?

Any idea which CSS code I need to use to get that done (while waiting for the new version)?