In this case, these values are expressed as constants with a start of 0, an end of 300 and an increment of 20. The end of the block is indicated by the END FOR command. In the context they were used they had to be numeric. There is a default output format for all variables which may not be precisely what was wanted, but allows a very quick result to be produced. There are no comments in the program, nor any indentation to indicate which commands are in the loop and which are not.
All commands start in column one and periods are used to indent for readability.
Indentation and the use of one command per line is recommended. The C in column one indicates a comment. The 12T specification specifies that the next field starts in position 12.