I figured it - would be useful for others, who needs to modify
File to change : 'CloudZoom.CSS'
File Path : {root}\Plugins\SevenSpikes.Plugins.CloudZoom\Themes\Motion\Content\ folder.
Note : the path 'Motion' will change depending upon the theme you are using.
change the line-height: pixel under .gallery.picture-wrapper
whether this issue is resolved if so how this was rectified, i am facing same situation.