If I understand your question:
There are: 1000 / 3 =333 numbers that are multiples of 3
First number =333 / 1000 x second number =332 /999 x third number =331 /998 x fourth number =330/997=[333 / 1000 x 332/999 x 331/998 x 330/997] =12,076,031,880/ 994,010,994,000==302203/24875150==1.215%