There need not be any estimated digit: there could well be exactly 4500.
o
um, about 4500
4500 of them.
There need no be any estimated digit.
4500
The last digit is always the estimated digit in a number
There are 4500 such numbers.
There need not be any estimated digit but, if there must be one, then it is the last digit: 3.
500
4500
10,800
estimated 4500