Silvio placed a number above the 1 in 142 because in the addition, he was adding two numbers that resulted in a sum that exceeded the value of a single ten (in this case, 4 tens from one number and 9 tens from another).
The correct response would be:
The sum of 4 tens and 9 tens is 13 tens, which is regrouped as 1 hundred and 3 tens.
This means that the extra 1 (representing 100) was placed above the 1 of 142 to represent this regrouping.