It has 6, you are missing the *raw* type. Appreciate you might not want to introduce this as it is unlikely that novices will use it, but if you leave it out, perhaps update the line to read

> `R` has 6 basic atomic classes, the most commonly encountered being

and then you could leave off the complex type as again, most users are unlikely to come into contact with it.

Might also be useful here to explain what is meant by "atomic" - it'll come up again when the students look at matrices/arrays.