Don't worry. The man pages seem a bit rough to handle for a while, but you just have to stick with it. The echo and time man pages are relatively simple. You can always just experiment as well. The echo command isn't going to crash your computer

It's all a part of learning the ropes.
As for the quotes with the echo command, they actually aren't necessary. I add them out of habit. This will do the same thing:
Code:
echo -ne ${percentage} ${other_data}\\r
The only difference is an extra backslash. The reason for that involves how bash tries to interpret/process commands entered before actually executing them. The details aren't that important. Just keep in mind that if you use a backslash
outside of double- or single-quotes, then you may have to sprinkle in some more backslashes to make things work as expected.