I'm unsure of the correct notation here so please bear with me.
Provided that x is a positive integer:
will produce a number which is 1 followed by x 0's. What I mean is that:
, which is 1 followed by 0's
which is 1 followed by 0's
will be a 1 followed by 30 zero digits.
If x is greater than one, as it is in your case, and an integer, it will end in 10 and be preceeded by (x-2) nines when 90 is subtracted.
x-2 = 4
The result is four 9's followed by 10.
There are 7 nines followed by 10.
So in your example:
You will have 28 nine's followed by a 10.
The sum of the digits will be:
which is, as you say, 253