Hi, Michael 

Firstly, I would like to sincerely apologize for the delayed response as we have been experiencing an unusually high number of tickets. I am sorry that it has taken longer than usual to respond to your concern and your patience is highly appreciated.

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Yes, we don't have a built-in option to add suffix/prefix for charts,

thank you for that suggestion, we will do our best to work our way through all of the requests from our users.

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At the moment, the logic for this for the charts is like this :

This can't be inherited from the table's prefix or suffix, so you will need to use wpDataCharts callbacks to display the percentage.

Take a look at this page, where we explained how this can be added on a chart with two Y axes. The same logic applies to one axis.

• Every chart exposes several options that customize its look and feel. Charts usually support custom options appropriate to that visualization. wpDataChart callbacks allow adding options that are available in Google Charts API, Highcharts API, and Chart.js API. 

• All necessary resources are available in charts engines API (depends on which one you use). Every engine has a different approach to chart settings. In wpDataChart callbacks, you have to adopt those settings to the wpDataChart object (you can take a look at examples for each engine in our documentation, and also in the Support help center). A huge number of examples for any area of programming can be found on stackoverflow.com (typing your problem in google and at the end add "site: stackoverflow.com" and Google will search only that website). Also, a lot of examples of charts, chart settings, and customization can be found on jsffidle.net (typing in google for example "line chart highcharts jsffidle")
• Please note that using hooks or wpDataTable and wpDataChart callbacks requires a certain level of programming skills and included support refers only to advice.