Hi Daniel,
You can customize the "Grand Total"
text in the pivot table by modifying the localization text in the resource
files. For your convenience, we have provided a sample demonstrating how to
change the "Grand Totals" text for the "en-US"
locale (the language code for English - United States). Please refer to the
screenshot below for further details.

Output screenshot:

In the meantime, we have provided a runnable sample for your reference.
Please find it in the attached file below.
Furthermore, you can refer to the following UG documentation for more
information on localization.
https://blazor.syncfusion.com/documentation/common/localization#adding-culture-based-resx-files
Best regards,
Sridhar Karunakaran
Attachment:
SyncfusionBlazorApp3_27f1b71c.zip