Issue in reports grouping shows users group multiple times sugarcrm 6.5.11

I have created a report for user wise calls wise disposition (custom field) and in output I got result multiple user groups for few users while on chart its a single vertical bar with accurate total of 2 groups found below for that same user.

Matrix Report created on calls,

Groups :User Name, Call Disposition 

Chart : Vertical Bar

How could we resolve this?