In the context of advice about whether to show animation while giving a speech, the sentence
- It's easier to dial it down than ramp it up.
means that moving from extreme animation to less animation is easier to do than becoming more animated after showing little animation at first.
The meaning is conveyed by metaphor.
Dial down and ramp up are phrasal verbs, which take pronoun objects between the verb and its particle. The object -- it -- refers to the same thing in each case -- animation while speaking -- and the opposition of up and down as particles for the phrasal verb shows that they are opposites.
They are also both metaphors, and not the same metaphor, which makes it confusing.
Dial refers to a volume knob on an old radio or stereo (supplanted by icons to press on newer equipment). Turning the knob, or dial, raised or lowered the sound volume. Dialing it up raises the volume (this is an
UP/DOWN metaphor), and dialing it down lowers it.
A ramp, on the other hand, is a tilted surface for movement vertically. To ramp up something is to increase its height, which may simply mean providing a larger number, as here.
Consequently both turn up and ramp up have much the same meaning in this context, as do turn down and ramp down. So why use two? Good question.
Probably for variety. This is a motto that the listener is supposed to bear in mind, after all, and the punchier it is, the more likely they are to remember it. Or so one can hope.