Laravel Maatwebsite / PHPspreadsheet - how to get value format in Excel export

I'm using the Maatwebsite Excel package for Laravel 5.4 - http://ift.tt/1kdyvgZ

When exporting data from Laravel models, all the number and Carbon date values get exported as strings. How can I get these exported in the form of Excel 'values' (i.e. imagine using the =value() function in Excel)?

Thanks

via Chebli Mohamed