Bex variables and webi prompt screen

Hi All

Im currently using Webi (BI4.1) on top of BEx queries which have several variables defined within the BEx query.

Can someone please explain to me what determines the display of the prompt in Webi? IE sometimes the prompts show as text, other times key.

I cannot figure out what drives this initial display as generally users do not want keys shown by default. Any advice would be greatly appreciated

Thanks

Ryan