map visual: control sizing by hidden column

Ability to size the bubbles on the Map visual (globe icon) by a column that is not returned to the visual. I have a column where the importance of the value is inverse to the value itself.  For example: Sev 0 is actually the highest severity, while Sev 10 is the lowest.  
 
I have created an additional column and assigned inverse values to these Severities and used this column to control sizing of bubbles on map, but I don't want to display these column values as they do not mean anything to users.