% of max calculation changes on context.

I've noticed that the context of the % of max calculation changes depending on if you have 'values' in the columns drop zone or not.   When included it separates the calculation by column (each column '(total)' = 100%).  When 'values' is excluded from the column drop zone the context of the calculation changes.

 

 

 Can anyone explain why this happens ? and if its expected behaviour.

 

Thanks

Katie