4 Answers

Two decimals means that the unit number has a partial unit.  Like 2.5 is two and one half.

When you do tow decimals that means two numbers to the right of the decimal point.  Example 2.75 is 2 and 3/4 in decimal usage.

Seeing the other answers, maybe I misunderstood the question.

If you are referring to something that looks like this:      246.57...... the number(s) to the left of the decimal point represent two hundred forty-six.  The numbers to the right of the decimal point represent 57/100 of 1.  DECI is a prefix for 10; our number system is based on 10. 
Each digit in a number has a "place value".  The 2 in our example represents "hundreds" (in this case 2 hundreds, or 200).  The 4 represents 4 tens, or 40.  The 6 represents "ones" or 6.

The 5 represents 5/10, the 7 is 7/100.  To extend the number  246.57981.....the 9 represents 9/1000, the 8 is 8/10,000, and the 1 is 1/100,000.

That number would be read as follows:  Two hundred forty-six and fifty-seven thousand, nine hundred eighty-one     hundred thousandths.

Is this what you were asking?

could also be percentage..

Very Good answers provided above. They are absolutely correct in mathematics. I understood the question in another way. In software there could be the use of two decimals in a number (ie 2.1.1) which is software versions. This is the only way two decimals can be used in a single string of numbers.