FOR COUNTER = 0 TO 10 STEP 2
  PRINT "Counter:", COUNTER
NEXT COUNTER
'
END

Counter:  0
Counter:  2
Counter:  4
Counter:  6
Counter:  8
Counter:  10

In this program, the STEP 2 means to count upward "by twos."

Syntax of the FOR Statement (with STEP)

Here is the syntax when STEP is used:

FOR counter = startingValue TO endingValue STEP stepSize 
  loopBody
NEXT counter

The list of rules changes just a little:

counter is a numeric variable.
You can use counter in the loopBody, but you should not try to change it (because it changes automatically.)
startingValue, endingValue, and stepSize can be arithmetic expressions or variables.
loopBody can be any number of statements.
NEXT counter shows the end of the loop body.

This program follows those rules:

LET C = 0
LET START = 2
LET FINISH = 10
LET SIZE = 2
'
FOR C = START TO FINISH STEP SIZE
  PRINT C;
NEXT C
'
END

In this program, stepSize is the variable SIZE. That is OK.