Styling the Size (Custom Field) input for iPhone?

[kostianev]

Hello, I need to style my Custom Field input with Size for Mobile Telephone. Please, see the VIDEO recorded what I mean. https://goo.gl/x4zov9
See the first that the inputs from Filter menus are visible very good on my iPhone, but the Size input is not the same. I want to make this like others, goes down on all screen, how to achieve this?