Actually, int(random(10,21)) with give you values from 10 and including 20.
Indead.
int() and floor() works the same in this case, it round down int(5.6) = 5, floor(5.6) = 5.
You can also use round(x), it will round to the closest integer number, round(5.6) = 6, round(5.4) = 5.
round(random(10,20))
:)