A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
Hi Sinthanun,
I understand you are working in Excel for web and you want to use Distinct Count option to summarize value in Pivot table.
To use Distinct Count option, one should add the data to Data Model. We can insert PivotTables in Excel for the web spreadsheet but to create Power Pivot data models, we will need Excel desktop application.
Reference: Excel for the web
Distinct Count option is available of Excel 365 desktop application, but not in online version.
There are certain differences when working in Excel for the web and desktop application, to know more about it, please see Differences between using a workbook in the browser and in Excel
We appreciate your understanding.
Regards,
Neha