Excel web access WebPart losing chart formatting

Hi Experts,

Currency-Formatting is getting lost when showing Excel-Sheet in Excel Web Access WebPart, added to a Wiki-Page in SharePoint 2013 (On-Premise SP1). The Format is correct in Excel Client but lost in SharePoint. See following Image with a minimized example:

Is there any hint how to get the Format shown up in SharePoint?

Best Regards, Ronny