This field is read-only and is automatically assigned when you save a line in the table. Line # is very important because formulas are always evaluated from the top of the table downward. Lines that reference other variables or calculations need to have a higher Line # than the lines they refer to. Generally, variables that users will enter at run time will appear at the top of the table and thus have lower Line #s.
There are three basic options for data in this field. They are:
Empty. The user will be prompted to supply a value at takeoff time.
A number.
A logical expression composed of numbers, mathematical operators, functions, and variables defined previously in the formula. To be called out in an expression a variable must have been defined in a line above the current variable and the variable name must be enclosed in brackets.