GRT - Grand Total
INV - invoicee, add the invoicee number at the end. Example: INV20 to show invoicee number 20, INV0 will show items not assigned to an invoicee, INV-1 will show all items from the booking regardless of invoicee. You can combine INV[BOOKINGINVOICEEID]] to add the invoicee from the booking
LAN - language. Example LANDE will force the language to German