It depends on what you want to achieve. As I know ArchiCAD is using meters inside if the system. So every time when you are using feet and inches - it converts them into meters.
If you want to convert your A into feet and inches and show only inches without " symbol as a string, then first question - what would you like to get, if A has feet too - let say it's 1'-6"? Will %fi - fractional inches - not show feet? Also, if it's fractional inches - what will happen when you have let say 1/6"?
All these questions necessary to ask that script wouldn't collapse when A is changing.
Width = STR ("%fi", A)
will give you 6" - as a string. You can use SPLIT to separate 6 from "
n=SPLIT(Width, '%n"', widthNum, string)
widthNum will be equal 6 (number)
but if it will be 1/6" then maybe better to cut " from the end:
len = STRLEN(Width)
WidthNum = STRSUB(Width, 1, len-1)
So, first, we are getting the length of the word (1/6") - i.e. 4 symbols.
Then we are showing from the first symbol until len-1 symbol (i.e. 3).
WidthNum = '1/6' (string)