Board Thread:Support Requests - Designing Your Wikia/@comment-24796040-20140410135539/@comment-168424-20140414224428

So that is the default Infobox template as you said. It would probably be better to make a copy of it and modify it.

The key wikicode is this: |- | style="width:30%;" |  | style="width:70%;" |

The  sets the header column width and the   sets the data column width. Just change these percentages in a copy of the template and use the copy.