the full extent of From the top of the Empire State Building, you can see the full extent of Manhattan (= the area it covers).

the extent of We don't yet know the extent of his injuries (= how bad his injuries are).

Rosie's teacher was impressed by the extent of her knowledge (= how much she knew).

in extent The River Nile is over 6,500 kilometres in extent (= length).

Approaching the airport, you could see the full extent of the island.

To some extent it was my fault, though I didn’t mean any harm.

We didn’t know the extent of his injuries.

It makes sense to a certain extent to write down everything.