Same as Title.

If your talking about the config option thats just for the spawned dragon.

How can I adjust that 10000 to 500? It give too many burden to server.

You cant. And it shouldn't cause any trouble for servers. It could be 500 or 500000 and it shouldn't make a difference because the end is void. Meaning nothing to generate and nothing to save. Unless you have something installed that adds structures to the end such as Hardcore Ender Expansion. but even then its still much less then a normal world.

Okay. Thanks for Answer.