Could this be an exercise in learning to co-exist with fussy programming languages? Were you told to use a particular variant?
We learned Fortran programming in school circa 1970. It was fussy about syntax of the PRINT statement. You had to designate the number of columns for integer and fractional portions. (Later Fortran versions are not so fussy.)
When we wrote a single long mathematical calculation, we found it's easy to make a mistake. Therefore it's wise to do a calculation in segments, breaking it up over several lines. Then if we made a mistake, the compiler tells us exactly which line has the error.
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Every line had to be numbered. It's a good idea to do them in increments of 10, because it's inevitable you'll want room to add more lines in between, as you revise your program.
This is not correct; we need to label the statement with number (numeric label) if that particular statement is a target.
I learnt FORTRAN around the same time (1974); the only other computer programming languages suitable for scientific computations was ALGOL (that was popular in the Europe). I used FORTRAN till 1984 and then changed over to PASCAL and then to C. I still consider FORTRAN a good programming language for scientific work and even today thousands of scientists use fortran routinely.
Then I guess I used an earlier version. The punch cards had to be in sequence. Line numbers were essential in case the cards got out of order, which was easy to do.