The term is dry to touch. There is a window with paints when it can be recoated and when it can't. This window is caused by the solvent 'drying' process. If it is recoated after the initial start of this period, there is risk of the top coat trapping the evaporating solvents in and bubbling. When coated before the start of this period, the top coat and sub coats fuse solventwise as one.
One thing to consider is the directions are based on 70 deg and low humidity with high airflow. In a colder setting it can take a lot longer, but if heat can be added (as much as 350 is alright) it can accelerate the process to mere hours. That is how production lines can do it so fast. Not to mention it makes the enamel a ton harder to scratch.