Hi Mike,
Thanks for your interest in syncfusion products.
To remove the text value from annotation, you could simply set the series annotation description as null.
serAnnot.Description = "";
Since you say that you use a Symbol I suppose its AdornmentInfo used rather than the Annotation.
To remove text from AdornmentInfo you could use a LabeTemplate with no value for the TextBlock as shown below.
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Please refer to the below given link for both the samples.
http://files.syncfusion.com/support/Chart.WPF/7.3.0.20/F88637/main.htmPlease let us know if you have further queries.
Regards,
K. Saradha Devi