Hi Hoang,

Before you save the data to a datastore, please set the decimal number column's meta info like this:

use \koolreport\processes\ColumnMeta;

...
  ->pipe(new ColumnMeta(array(
  		"column1"=>array(
  			"type" => "number",
			"decimals" => 2,
			"thousand_sep" => ",",
			"dec_point" => ".",
			"prefix" => "",
			"suffix" => "",
  		),
  )))
  ->pipe($this->dataStore('dataStore1'));

This should help the excel export process format column1 to a decimal number. Please let us know if there's still any problem. Thanks!