I think you are reading the tutorial too literally. The turorial does say
for VARIABLE in 1 2 3 4 5 .. N
but taken literally this is not correct bash syntax - I think the author is simply trying to say that for this kind of for loop you need to explicitly list out all values you need to iterate over. So in your case this would be:
for var in 0 1 2 3 4 5 6 7
The tutorial also mentions brace expansion, which @glennjackman gives in his answer which is also entirely correct syntax.