Bought the car in May21 and have done about 3000 mile. The AdBlue warning came up say to add some within 1034 miles.
On the info it showed two green blocks and a small green sliver.
I got 10 L of Redex AdBlue from Toolstation @ £9.99 and put the whole lot into the tank, which was very easy. NB this stuff is meant to be very corrosive so I wore gloves and had rags at the ready.
The info now has 6 blocks eg about 3/4 full. The owners manual says the AdBlue tank is 17 L
Hope this helps