But presumably it can sink 0.33 mA? Page 384 of the datasheet says the pins can sink 20 mA (as tested) but more is likely.
Although each I/O port can sink more than the test conditions (20mA at VCC = 5V, 10mA at VCC = 3V) under steady state conditions (non-transient), the following must be observed:
and it goes on to give limits for the entire port…