How can i set in the regions manual H or W

Hi, how can i set a manual H or W with the upfront child theme, it's hard to set the correct values...
For example, to the buttons or something else in the editing if i need to set a personal and same value for that, I used the drag and drop and normally it's works, but if this didn't work...?and i don't know why if i set for the body region 1080px, why the upfront didn't manage the rows like 1/1 ; 1/2; 1/3; 1/4 and the anothers sizes, i need to drag and drop the size and it's hard to set the perfect value for me.
Another, I didn't understand why i cannot set for the groups a personal css for that, with the personal css in the groups i can set all the sizes that i need. Or set a left and right padding for that. If i like to change this value, i need to mapping the css outside the upfront for see what's happend with this css strings...
Or why i cannot set also a manual value for the rows, and I only can managed them with the drag and drop... Sometimes I can't set the correct value and the theme didn't work properly with the responsive...