Missing Translationoption for "Grand Total"

Hi,

i used to translate the Plugin to german using poedit. Nearly everything worked well, but in the po file is an entry missing for “Grand Total”, so i cant translate it.
How can this Word be added to the po file?
Must this be added to your source PO-File?

Thanks!
Volker

https://wordpress.org/plugins/woocommerce-pdf-invoices/