The PopulateHeaders will not handle setting values in column headers.
You can use code like this to set values in the headers without triggering events.
string[] headers ={"trans","count","min","max","mean"};
int row = 1;
int col = 1;
foreach(string s in headers)
{
GridStyleInfo style = new GridStyleInfo();
style.Text = s;
this.gridControl1.SetCellInfo(row, col, style, Syncfusion.Styles.StyleModifyType.Override, true, false);
col++;
}