Since its impossible for there to be more than 40 total wickets (for both sides) in a 5-day match, the "66 wickets" example might be a tad unrealistic.
However, what I think you might be trying to say is...
"What does it mean when they say that Australia is 66 for 4?"
The answer is...Australia is batting, and they have scored 66 runs while losing four wickets. Four of their batsmen have got out in the course of scoring 66 runs. Which really isn't a good thing, because the batsmen at the top of the batting order are supposed to score more runs than that. Especially Australia, who are very good at scoring runs. But I'm rambling now.
Thank you. That makes sense.