Plant height

Hi when they say "Grow Height : 60 cm" what it means ?
its the height that we must reach before flowering ?

who is "they"?

The sites that selling seeds

That's the fully mature height

So when say 60 cm its good to veg the plant until 40 cm right ?

let it veg until about 12" or more, depending on that you can either let it grow heigher or better to top it, then flower it