To play:

• Press R. It selects the answer, which you need to work out. Wait until R is lit.
• Now make your first guess, then E. The number of digits entered determines the difficulty (3/4/5).
• The NUMBER column indicates how many correct digits you entered (but not which ones).
• The SEQUENCE column indicates how many of those digits are in the correct place.
• Note: if you entered a digit more than once (example 222), and there is a 2 in the answer, it will show 3 correct digits.
• Enter your next guess, then E. If you enter the wrong number of digits, 1 will flash.
• If you take too long, R will start to flash.
• When you get the correct answer, all the numbers flash. Press R for another game.

Here's the Comp IV Manual.