“There's not that much to it, really.”
You know how to juggle. Now you're showing your nephew how to do it. You tell him that it's not as hard as it seems.
There's not that much to it, really.
"Not that much ___" means "not very much" or "not as much as expected". For example:
Do you want the rest? There's not that much left.
A: How much is it?
B: It's not that much. Just 25 bucks.
Use "not that much" in spoken English.
"There's not much to it" means that something is simple and easy. You can use this phrase when you're explaining how something works:
You just flip that switch and wait. There's not much to it.
When you end a sentence with "really", it sounds like you're being extra-honest. You're sharing an opinion that's a bit of a secret between you and the speaker.
It's not that big of a city, really.
I'd prefer to stay home, really. But my husband loves to go out to eat, so I go with him.