From 02.02.2022 onwards, the country code must be entered as the starting country at the first possible parking place after crossing the border.
The legislation:
From 2 February 2022 the driver shall also enter the symbol of the country that the driver enters after crossing a border of a Member State at the beginning of the driver’s first stop in that Member State. That first stop shall be made at the nearest possible stopping place at or after the border. Where the crossing of the border of a Member State takes place on a ferry or train, the driver shall enter the symbol of the country at the port or station of arrival.