Yes. It's very simple, and not very accurate - it is meant as fun, nothing more (although it is mentioned in the nag to purchase when the trial ends). Each action that runs has some amount of time saved guessed for it, which might vary depending on what it does.
Which means you could create a macro that did nothing a lot, like say:
- Repeat 100000 times
- Set Variable X to “hello”
And Keyboard Maestro would “save” you a lot of time.
Clearly there are lots of actions that give too much timed saved, since it is farcical to think that Keyboard Maestro has saved anyone 278 years.