Is "Customer" a "Customer ID" number or is it an already aggregated number/count of Customers?
Please see newly attached workbook v.10.3 and below screenshots as to what was done to get there...if this answers your question, please respond to the original post and mark it as correct so that others can possibly use it in the future.
This is the traditional method of doing a COUNTD on your customer, however, a pie chart won't work with this method, hence the need for an LOD calculation which performs similarly but also allows for a pie chart.
This screenshot shows the LOD Calculation and that Customer was moved from Measure to Dimension.
Then changed the calculation to a quick table calc as % of Total:
Then used the "Show Me" chart of tables to create a pie chart, added labels appropriately.
Hope it helps...again, if yes, please mark the original posting as correct. Thx, Don
pie chart(DW)_v10.3.twbx 28.4 KB