Export Data Store Entity to Excel Smart Service - Custom Cell Positions throwing error

My goal is to write into excel in multiple sheets using the "Export Data Store Entity to Excel" ability.

I may write few values from process variables too into the excel sheet - apart from what I have in the database.

So I have an excel sheet as template and wanted to leverage the "Custom Cell Positions" and "Custom Cell Values" ability in the "Export Data Store Entity to Excel" smart service to put in the values in the desired position of the excel sheet. I may end up putting atleast 50 values in a sheet.

But I keep getting this error, even when I attempt to put couple of values using the "Custom Cell Positions"
"Custom cell positions cant refer to cells below the starting cell. Otherwise, they would be overwritten by data being exported. (APNX-1-4505-037)"

I tried to use this simpler option too and still get the same error.
Custom Cell Positions={"A6", "B6", "A7", "B7"}
Custom Cell Values={"Value for A6", "Value for B6", "Value for A7", "Value for B7"}

My excel template does not have any values beyond the 2nd row.

Does the "Custom Cell Positions" and "Custom Cell Values" ability really works when we attempt to write into an excel template (excel template name is mentioned in Document to Update").
This does not work even when I use the "New Document Name" option.

Any input is appreciated