Suppose you have a variable whose exact value is not known. Repeated estimations give values which match up to a certain degree but beyond that they are different. You could take some sort of [weighted] average of the leading digits of these different parts and your estimate for the variable wold be the matched part with the estimated digit appended.
For example, if you Google "mass of proton" the WIkipedia site give it as 1.672621898(21)×10−27 kg. The (21) - in parentheses - indicates that those two digits are estimated.
There need no be any estimated digit.
It is always the last digit.
0.503..the 3
The 7
The last one.
the estimated digit in 0.0782m is?
There need no be any estimated digit.
The last digit is always the estimated digit in a number
There need not be any estimated digit but, if there must be one, then it is the last digit: 3.
500
There need not be any estimated digit: there could well be exactly 4500.
It is always the last digit.
.0002 is the estimated number
It is 0.08 M
It is the zero at the end.
None of the digits need be estimated.
0.503..the 3