When are you supposed to declare money at the airport, when it reaches the maximum limit or exceeds it?

When flying to China, the maximum amount of cash you're allowed to go through customs with is "cash equivalent to US$5,000 or above". Does that mean I have to declare $5,000 or only when it exceeds it?

You will need to declare it if you have more than the $5,000.

That depends on the regulations of the country you are entering. Most countries do not check how much money you are carrying when you leave a country.

China requires those entering China to declare the equivalent of $5,000 US or higher. And, if you have, say, $4,995, they will look at that as trying to sneak in under the limit.

5000 or above. Gee could that mean you have to report 5000? Does it say more than 5000?
Do not go to China unless you can understand and follow rules.

You have to declare anything over ten thousand and they are going to want to know where you got any large amount.

It is a limit, you should gauge how close you are to it, and whether you want to be singled out for inspection at customs and they discover the cash and then need to verify if should have been declared. If it was gained legitimately then you will be fine declaring it, and just take proof, i.e. Bank statement or any other documents showing receipt from source.

You have to declare $5000 and anything above that.

EX: You have $4999.99 in your small change purse. Don't declare it.
EX: You have $5000 in your small change purse. Declare it.
EX: You have $5001 in your small change purse. Declare it.

What part of "$5,000 OR above" makes you think you wouldn't have to report $5000?

Your question would make sense if the wording about cash said 'cash higher than $5,000'. Then you might reasonably wonder if you should declare $5,000.
But it doesn't. It says '$5,000 OR more'. Therefore you should declare $5,000 AND anything higher.
The answer from @oldprof is as clear as can be.