Hi Padma,
Thank you very much for your patience.
We are afraid that we are not able to reproduce the issue "Setting the number format to 'text' format and then applying the template marker does work" from side. We have created the simplified sample to apply the number format to 'text' and applying the template marker with 'copystyles' option. We have shared the sample below. Please make use of this and let us know if this helps you.
Also we have shared the updated online help link of template marker below.
http://help.syncfusion.com/ug/asp.net/xlsio/default.htm#!Documents/templatemarkers.htm
if you still reproduce the issue, please modify the above sample to reproduce the issue and revert back us with the same. it would help us to investigate further on this.
Please let us know if you need any clarifications.
Thanks,
Manikandan M.
TemplateMarker_484c6e73.zip