I'm not sure I'm understanding what your question is. I will attempt to answer it, and you let me know if I have missed the mark.
[braille]#15 in +25 in .k #40 in
abbreviations must be spaced away from the associated number and from operation signs. So there is a space on both sides of "in"
no spaces need be inserted when words represent the values to be added/subtracted/etc.
[braille]=ty-two+forty-two .k eighty-f\r
In the example with a combination of numbers and words there should be a space between the number and the word that follows it, but no space between either the word or the digit which comes before or after the operation sign.
[braille]bin>y #1011 .k #1 eight+0 fours+1 two+1 "o
no contractions in words that touch operation signs or those that precede or follow a comparison sign
edited by dworthing on 11/3/2009