It’s not really about “what things can be”, it’s about the way something is being talked about – the context.
More words are required: the percent symbol just means “divided by 100” or “out of 100” or “100ths”, and so there is more context needed before it makes sense to talk about numbers greater than 100% or not.
“I am going to give 112% of my own time to this project.” probably makes no sense, because 100% would be all of the speaker’s own time he could have to give.
That is, it makes no sense when the context is talking about how much of something limited that can’t be more than all of it.
In other contexts, there is no problem. If you have 50% more eggs than Ted, who has 10, how many do you have? 15. What percent more than 10 would 500 eggs be? 4900% more.