That's true yes. But the reason for that outnumbered attack by the Brtis was that they were surprised (apparently) and needed to make hasty actions before the Argentines could fully conquer and fortify the islands. Strictly speaking, the Argentines were the attackers and the British the defenders.
It should be noted though also that the British forces were much better prepared and more professional compared to the Argentine ground forces who were subscripts for a large part, sent into combat with only minimal training (some of them had shot only about a hundred shots on the range before being shipped to the Falklands). Argentine had hoped there wouldn't be any combat at all. Bad guess.
The sea warfare was a bit more even.