Total column value for my table is not automatically updated


I am trying to calculate column values from Table

For my numeric label, I am using below expression.

sum({},“GRS Lit”)

My table are bind to a few different dataset tag.
So below is my first dataset (lets call it dataset1).


And once I replace with dataset2 (without any values inside) for my table, seems like the numeric value still not updated. It still holding the previous value


Wondering why it does not show 0 when I already removed the value in Row 1 and 2 ?