Your dryer probably has a humidity sensor in it. The more dry makes the machine go beyond where it would normally stop. Optimum dry is the “perfect” balance of humidity left in the clothes for texture and wrinkling, and less dry is just that, more humidity left over. The less dry is for stuff like polyester and for clothes that are heat sensitive or that you want to hand iron a few hours later.
It’s probably some combination of time and heat level. You’ll want a longer cycle for things like jeans and towels, shorter for t-shirts etc.
I always like to start with a shorter cycle since it uses less energy- if things are still wet after, just set it to run a few more minutes, if they’re dry, then you haven’t wasted any energy.
It’s nearly impossible to burn clothes in a household dryer unless something is really broken.
its just the amount of time your dryer will run for more dry is longer than less dry. be careful you dont overdry and burn your clothing
Dry, drier, driest.