X is an accurate value, called a sum.
(2a+2b+2c+2d+...) is an inaccurate value < X, and it is called (and here comes a novel concept) a fog.
Fogs are only approach to a given sum (what is called by you a limit).
For example: pi is a sum, and it is used by Standard Math as the limit of fog 3.14...[base 10], where fog 3.14...[base 10] < pi (fog 3.14...[base 10] only approaches sum pi).
In order to reach pi, one simply "jumps" form any arbitrary chosen scale level straight to sum pi, but then fog 3.14...[base 10] < pi is not found anymore, and we get a sum, which is based on finitely many segments AND points that have sum pi.
This novel reasoning about infinite convergent series is clearly demonstrated in
http://www.internationalskeptics.com/forums/showpost.php?p=5721761&postcount=9104.
In other words, sums are local numbers, and fogs are non-local numbers.
By OM the place value method is a fog if infinitely many scale levels are involved.
By Standard Math the place value method is a representation of a sum (fogs are not found under the Standard framework).
Since Standard Math paradigm does not deal with fogs, then X can't be but a sum.
By using the limited reasoning, one simply can't get (2a+2b+2c+2d+...) as a fog (called also a non-local number, under OM).