Dear Ali Akbar

Step 1.) The solution was to add the following JavaScript into the Function and Global Variable Declaration.

Step 2.) ig_total_sum is the static ID of the Interactive Grid.

Step 3.) Paste the code

function renameOverallSumToTotal(spreadsheetID)
{
var g = apex.region(spreadsheetID).widget().interactiveGrid('getViews', 'grid');

var labels = g.view$.grid('option', 'aggregateLabels');
labels.SUM.label = 'Subtotal';
labels.SUM.overallLabel = 'Total';
g.view$.grid('option', 'aggregateLabels', labels);

g.view$.grid('refresh');
}

// Rename the totals rows on both spreadsheets
$('#ig_total_sum').on('interactivegridviewchange', function(event , ui)
{
renameOverallSumToTotal('ig_total_sum');
});