In your first BUILD you were using "columns", but columns which, except for the last, would cause overwriting of data from the BUILD, which is not allowed.
You want one space between your first fields. Two main ways: columns or specifying a space.
BUILD=(1,8,X,10,7,X,18,5,X,24,2,42:27,10,11X)
I agree with enrico. You will get more by looking in the manual for the BUILD posted than by anyone just telling you what it does. If, after reading the manual and experimenting, you still have questions, post what you have understood, and the problem you still have, and someone will assist.